Power Factor Calculator
Calculate power factor from kW and kVA, kW and kVAR, volts, amps and watts, or phase angle, and find the capacitor kVAR to reach a target PF.
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How the Power Factor Calculator Formula Works
Power factor tells you how much of the power flowing in an AC circuit does useful work. Real power, in kilowatts, is what turns a shaft or heats an element. Apparent power, in kilovolt-amperes, is voltage times current. The ratio of the two is the power factor: PF = kW / kVA. It runs from 0 to 1, and 1 means all of the apparent power is doing work.
The two are tied together by the power triangle. Real power kW is the base, reactive power kVAR is the height and apparent power kVA is the long side, so kVA squared equals kW squared plus kVAR squared. The angle between the base and the long side is the phase angle between voltage and current, and the power factor is its cosine. That gives several routes to the same answer. With kW and kVA, divide. With kW and kVAR, find kVA first. With volts, amps and watts, the apparent power is V x A for single-phase and 1.732 x V x A for three-phase, then divide the watts by it. With an angle, take the cosine.
Power factor correction adds capacitors to supply the reactive power locally. To move a load of known kW from PF1 to PF2 you need kVAR = kW x (tan(acos PF1) - tan(acos PF2)). The same kW then needs less kVA, so the current falls by the ratio PF1 / PF2. Automatic power factor correction (APFC) panels switch capacitor stages in and out, so the calculator also tells you how many stages of a chosen size you need.
PF = kW / kVA = cos(angle) | kVA squared = kW squared + kVAR squared | PF = W / (V × A) single-phase, W / (1.732 × V × A) three-phase | capacitor kVAR = kW × (tan(acos PF1) − tan(acos PF2))- kWkWReal power, the part that does work.
- kVAkVAApparent power, volts times amps divided by 1,000 (times 1.732 for three-phase).
- kVARkVARReactive power, the part that moves back and forth and does no work.
- PFratioPower factor, kW divided by kVA, from 0 to 1.
- angledegrees25Phase angle between voltage and current. PF is its cosine.
- + 1 more input below
- kW
- kW
- Real power, the part that does work.
- kVA
- kVA
- Apparent power, volts times amps divided by 1,000 (times 1.732 for three-phase).
- kVAR
- kVAR
- Reactive power, the part that moves back and forth and does no work.
- PF
- ratio
- Power factor, kW divided by kVA, from 0 to 1.
- angle
- degrees
- Phase angle between voltage and current. PF is its cosine.
- PF1, PF2
- ratio
- Present and target power factor for a correction.
Using the Power Factor Calculator
Enter calculate power factor from
Choose from kW and kVA, kW and kVAR, Watts, volts and amps, Phase angle, Capacitor kVAR to reach a target PF.
Enter real powerkW
Type the figure you already have, then press Calculate.
Enter apparent powerkVA
Type the figure you already have, then press Calculate.
Enter real powerkW
Type the figure you already have, then press Calculate.
Enter reactive power (size of the kvar)kVAR
Type the figure you already have, then press Calculate.
Enter supply
Choose from AC, single-phase, AC, three-phase (line-to-line voltage).
Enter real powerW
Type the figure you already have, then press Calculate.
Enter voltageV
Type the figure you already have, then press Calculate.
Enter currentA
Type the figure you already have, then press Calculate.
Enter phase angle between voltage and currentdegrees
Any value between 0 and 90.
Enter real power of the loadkW
Type the figure you already have, then press Calculate.
Enter present power factor
Any value between 0.01 and 0.99.
Enter target power factor
Any value between 0.02 and 1.
Enter capacitor stage size (kvar)kVAR
Type the figure you already have, then press Calculate.
Read the result
Press Calculate to update the result. Until you do, the last result is dimmed and marked as out of date, so you always know which numbers belong to the values in the boxes.
A Real Worked Example
A load uses 80 kW of real power and the supply carries 100 kVA of apparent power. The power factor is 80 / 100 = 0.800. The phase angle is 36.87 degrees.
The reactive power is the square root of 100 squared minus 80 squared, which is 60.000 kVAR. That is 0.750 kVAR for every kW, the 3-4-5 triangle scaled up.
150 kW and 100 kVAR
Choose the kW and kVAR option with 150 kW and 100 kVAR. The apparent power is the square root of 150 squared plus 100 squared, which is 180.278 kVA.
The power factor is 150 / 180.278 = 0.832, at a phase angle of 33.69 degrees. The reactive power is two thirds of the real power, 0.667 kVAR per kW.
Three-phase: 11,000 W, 400 V, 20 A
A three-phase load draws 20 amps at 400 volts line-to-line and measures 11,000 watts. The apparent power is 1.732 × 400 × 20 / 1,000 = 13.856 kVA.
The power factor is 11,000 / 13,856 = 0.794, with a phase angle of 37.45 degrees and 8.426 kVAR of reactive power.
A 25 degree phase angle
With a phase angle of 25 degrees between voltage and current, the power factor is cos(25) = 0.906. Reactive power per kW is tan(25) = 0.466 kVAR.
So a 100 kW load at this angle carries about 46.6 kVAR, and its apparent power is 110.3 kVA.
Correct 500 kW from 0.75 to 0.95
A plant draws 500 kW at a power factor of 0.75 and wants 0.95. The load has 666.667 kVA and 440.959 kVAR now. The capacitor needed is 500 × (tan(acos 0.75) - tan(acos 0.95)) = 276.62 kVAR.
After correction the apparent power is 526.316 kVA, and the current falls by 21.1 percent. With 25 kVAR stages you need 12 stages, which gives 300 kVAR installed.
Single-phase: 1,500 W, 120 V, 15 A
A single-phase device draws 15 amps at 120 volts and measures 1,500 watts. The apparent power is 120 × 15 / 1,000 = 1.800 kVA.
The power factor is 1,500 / 1,800 = 0.833, the angle is 33.56 degrees and the reactive power is 0.995 kVAR.
What Else to Know
How to Calculate Power Factor
Power factor is real power divided by apparent power, a ratio between 0 and 1. The calculator offers five ways to get it, because the numbers you have depend on the job. You can start from kW and kVA, from kW and kVAR, from watts, volts and amps, or from a phase angle. The fifth option does the reverse job: it finds the capacitor kVAR needed to raise a load to a target power factor.
Choose the option that matches your data, enter the values and read the power factor, the phase angle, the apparent power and the reactive power. The power factor table lists the angle and the reactive power per kW for common values, so you can check a result against it.
The tool treats the load as steady and balanced, which suits planning and learning. A meter will always show what is really happening.
Power Factor Calculation for Single-Phase and Three-Phase Circuits
For single-phase, apparent power is volts times amps, so PF = W / (V x A). A device on 120 volts that draws 15 amps and 1,500 watts has a power factor of 0.833.
For a balanced three-phase load measured line-to-line, apparent power is 1.732 x V x A, and PF = W / (1.732 x V x A). The 1.732 comes from the geometry of three-phase voltages, described in the Wikipedia article on three-phase power. Leave it out and the power factor comes out 73 percent too high, often above 1, which is impossible.
The kW and kVA, kW and kVAR and phase angle options work for any balanced supply, because they use total power rather than a single phase. The watts, volts and amps table gives examples of single-phase and three-phase results.
The Power Triangle, kW, kVAR and kVA
Real power kW, reactive power kVAR and apparent power kVA form a right triangle. As the Wikipedia article on AC power explains, the length of the long side is the apparent power. kVA squared equals kW squared plus kVAR squared. The angle between kW and kVA is the phase angle, and its cosine is the power factor.
That means any two of kW, kVAR, kVA and the angle give the rest. With 80 kW and 60 kVAR, kVA is 100 and the power factor is 0.8. The kVAR per kW column in the power factor table is the tangent of the angle, which is what the capacitor formula uses. Reactive power is covered in the Wikipedia article on reactive power.
The kW and kVAR option of the calculator applies this triangle directly.
What Is a Power Factor of 0.95?
A power factor of 0.95 means 95 percent of the apparent power is real power. The phase angle is 18.19 degrees, the reactive power is 0.329 kVAR per kW and the load needs 1.053 kVA for each kW. Compared with a power factor of 1, the current is 5 percent higher.
It is a common correction target. Many facilities aim for 0.90 to 0.95 or better, and some utility tariffs add charges below a set level. The level and the rule differ by utility and country, so check your own tariff.
A good power factor is not a safety figure or a legal requirement on its own. It tells you how efficiently the supply system is being used. Correcting all the way to 1.00 can lead to leading power factor and resonance problems, so 0.95 to 0.98 is often the sensible target.
Power Factor Correction and APFC Capacitor Size
To raise the power factor of a load, you add capacitors that supply the reactive power the load would otherwise draw from the source. The size needed is kVAR = kW x (tan(acos PF1) - tan(acos PF2)). The Wikipedia article on power factor describes how capacitors correct inductive loads such as induction motors.
The multiplier table gives the factor to apply to your kW for common starting and target values. Raising 100 kW from 0.80 to 0.95 takes 42.1 kVAR. An automatic power factor correction (APFC) panel switches the capacitor in stages, so the calculator divides the kVAR by your chosen stage size and rounds up. The stage table shows the count for several sizes.
The answer is a starting point. A real design considers harmonics, the voltage, the load profile and switching, and needs a qualified electrician or engineer.
Why Power Factor Affects Current, Capacity and Cost
For the same real power, a lower power factor means more apparent power and more current. At a power factor of 0.7 the current is about 43 percent higher than at 1. That current heats cables, takes up transformer and generator capacity and adds losses.
Correction frees that capacity. The current-reduction table shows what happens at several starting values. A 100 kW load at 0.75 needs 133.3 kVA, and at 0.95 it needs 105.3 kVA, a saving of 28.1 kVA and 21.1 percent of the current.
Whether that is worth money depends on your tariff, your equipment and your capacity limits. The calculator shows the electrical effect and leaves the financial case to you and your utility.
Accuracy, Limits and Electrical Safety
This calculator gives estimates for planning and learning. It assumes sinusoidal voltage and current, a balanced three-phase load and a steady operating point. Real systems have harmonics, varying loads and measurement error, and these change the power factor.
Do not use it alone to select capacitors, breakers, cables or protective equipment. Follow the National Electrical Code and local code, and have a licensed electrician or engineer size and install the equipment. Capacitors can hold a charge and are dangerous to handle.
For related tools, see the watts to amps calculator for current from power, the percentage calculator for checking a percent change such as a current reduction, and the linear interpolation calculator for values between rows of a table.
Reference Tables
| Power factor | Phase angle | kVAR per kW | kVA per kW | Current compared with PF 1 |
|---|---|---|---|---|
| 1.00 | 0.00 degrees | 0.000 | 1.000 | 0 percent more |
| 0.98 | 11.48 degrees | 0.203 | 1.020 | 2 percent more |
| 0.95 | 18.19 degrees | 0.329 | 1.053 | 5 percent more |
| 0.90 | 25.84 degrees | 0.484 | 1.111 | 11 percent more |
| 0.85 | 31.79 degrees | 0.620 | 1.176 | 18 percent more |
| 0.80 | 36.87 degrees | 0.750 | 1.250 | 25 percent more |
| 0.70 | 45.57 degrees | 1.020 | 1.429 | 43 percent more |
| 0.60 | 53.13 degrees | 1.333 | 1.667 | 67 percent more |
| 0.50 | 60.00 degrees | 1.732 | 2.000 | 100 percent more |
| Phase angle | Power factor | kW of a 100 kVA load | kVAR of a 100 kVA load |
|---|---|---|---|
| 0 degrees | 1.0000 | 100.0 | 0.0 |
| 10 degrees | 0.9848 | 98.5 | 17.4 |
| 15 degrees | 0.9659 | 96.6 | 25.9 |
| 18.19 degrees | 0.9500 | 95.0 | 31.2 |
| 20 degrees | 0.9397 | 94.0 | 34.2 |
| 25 degrees | 0.9063 | 90.6 | 42.3 |
| 30 degrees | 0.8660 | 86.6 | 50.0 |
| 36.87 degrees | 0.8000 | 80.0 | 60.0 |
| 45 degrees | 0.7071 | 70.7 | 70.7 |
| 60 degrees | 0.5000 | 50.0 | 86.6 |
| 75 degrees | 0.2588 | 25.9 | 96.6 |
| 90 degrees | 0.0000 | 0.0 | 100.0 |
| Present PF | To 0.90 | To 0.95 | To 0.98 | To 1.00 |
|---|---|---|---|---|
| 0.50 | 1.248 | 1.403 | 1.529 | 1.732 |
| 0.60 | 0.849 | 1.005 | 1.130 | 1.333 |
| 0.65 | 0.685 | 0.840 | 0.966 | 1.169 |
| 0.70 | 0.536 | 0.692 | 0.817 | 1.020 |
| 0.75 | 0.398 | 0.553 | 0.679 | 0.882 |
| 0.80 | 0.266 | 0.421 | 0.547 | 0.750 |
| 0.85 | 0.135 | 0.291 | 0.417 | 0.620 |
| 0.90 | none needed | 0.156 | 0.281 | 0.484 |
| Load (kW) | kVA at 0.75 | kVAR from 0.75 to 0.95 | kVA at 0.80 | kVAR from 0.80 to 0.95 | kVA at 0.95 |
|---|---|---|---|---|---|
| 10 | 13.3 | 5.5 | 12.5 | 4.2 | 10.5 |
| 25 | 33.3 | 13.8 | 31.2 | 10.5 | 26.3 |
| 50 | 66.7 | 27.7 | 62.5 | 21.1 | 52.6 |
| 100 | 133.3 | 55.3 | 125.0 | 42.1 | 105.3 |
| 250 | 333.3 | 138.3 | 312.5 | 105.3 | 263.2 |
| 500 | 666.7 | 276.6 | 625.0 | 210.7 | 526.3 |
| 1000 | 1,333.3 | 553.2 | 1,250.0 | 421.3 | 1,052.6 |
| Present PF | Current cut at 0.95 | kVA for 100 kW now | kVA for 100 kW at 0.95 | kVA released |
|---|---|---|---|---|
| 0.60 | 36.8 percent | 166.7 | 105.3 | 61.4 |
| 0.65 | 31.6 percent | 153.8 | 105.3 | 48.6 |
| 0.70 | 26.3 percent | 142.9 | 105.3 | 37.6 |
| 0.75 | 21.1 percent | 133.3 | 105.3 | 28.1 |
| 0.80 | 15.8 percent | 125.0 | 105.3 | 19.7 |
| 0.85 | 10.5 percent | 117.6 | 105.3 | 12.4 |
| 0.90 | 5.3 percent | 111.1 | 105.3 | 5.8 |
| Required kVAR | 5 kVAR stages | 10 kVAR stages | 12.5 kVAR stages | 25 kVAR stages | 50 kVAR stages |
|---|---|---|---|---|---|
| 30.0 | 6 | 3 | 3 | 2 | 1 |
| 60.0 | 12 | 6 | 5 | 3 | 2 |
| 100.0 | 20 | 10 | 8 | 4 | 2 |
| 150.0 | 30 | 15 | 12 | 6 | 3 |
| 276.6 | 56 | 28 | 23 | 12 | 6 |
| 400.0 | 80 | 40 | 32 | 16 | 8 |
| 750.0 | 150 | 75 | 60 | 30 | 15 |
| Supply | Watts | Volts | Amps | Apparent power (kVA) | Power factor |
|---|---|---|---|---|---|
| Single-phase | 1,500 | 120 | 15 | 1.80 | 0.833 |
| Single-phase | 1,800 | 120 | 15 | 1.80 | 1.000 |
| Single-phase | 4,000 | 240 | 20 | 4.80 | 0.833 |
| Three-phase | 11,000 | 400 | 20 | 13.856 | 0.794 |
| Three-phase | 30,000 | 480 | 45 | 37.412 | 0.802 |
| Three-phase | 60,000 | 208 | 200 | 72.053 | 0.833 |
| Term | Meaning |
|---|---|
| Real power, kW | Power that does useful work, in kilowatts |
| Reactive power, kVAR | Power that moves back and forth with the magnetic or electric field and does no work |
| Apparent power, kVA | The combination of the two, volts times amps |
| Power factor, PF | kW divided by kVA, equal to the cosine of the phase angle |
| Lagging | Current behind voltage, as with induction motors and transformers |
| Leading | Current ahead of voltage, as with capacitor banks |
| APFC | Automatic power factor correction, a capacitor bank switched in stages |
| Mistake | Effect | Fix |
|---|---|---|
| Using kW and kVA from different moments | PF is wrong or above 1 | Take readings at the same time |
| Leaving out 1.732 on a three-phase load | PF comes out 73 percent too high | Use line-to-line volts and 1.732 |
| Sizing capacitors from the nameplate PF only | Over or under correction | Use measured kW and PF at typical load |
| Correcting to exactly 1.00 | Risk of leading PF and resonance | Target 0.95 to 0.98 unless advised otherwise |
| Ignoring harmonics | Capacitors can overheat or resonate | Have the system studied by an engineer |
| Starting from | Formula |
|---|---|
| kW and kVA | PF = kW / kVA |
| kW and kVAR | PF = kW / √(kW squared + kVAR squared) |
| Watts, volts, amps, single-phase | PF = W / (V x A) |
| Watts, volts, amps, three-phase | PF = W / (1.732 x V x A) |
| Phase angle | PF = cos(angle) |
| Capacitor kVAR | kVAR = kW x (tan(acos PF1) - tan(acos PF2)) |
Frequently Asked Questions About the Power Factor Calculator
How do you calculate a power factor?
Divide real power by apparent power: PF = kW / kVA. If a load uses 80 kW and the apparent power is 100 kVA, the power factor is 0.80. You can also use PF = W / (V x A) for single-phase, W / (1.732 x V x A) for three-phase, or the cosine of the phase angle. Pick the matching mode above.
How to calculate PF from kW?
You need one more number besides kW, either kVA, kVAR, or volts and amps. With kVA, PF = kW / kVA. With kVAR, PF = kW / √(kW squared + kVAR squared). For 150 kW and 100 kVAR the power factor is 0.832. kW alone cannot give the power factor.
What is the 0.95 power factor?
A power factor of 0.95 means 95 percent of the apparent power does real work. The phase angle is 18.19 degrees, there are 0.329 kVAR for every kW and 1.053 kVA for every kW. It is a common target for correction and is often the level where utility charges stop.
How to calculate APFC?
Find the kVAR to add: kW x (tan(acos PF1) - tan(acos PF2)). Then divide by the stage size and round up. For 500 kW from 0.75 to 0.95 you need 276.6 kVAR, which is 12 stages of 25 kVAR, or 300 kVAR installed. APFC means automatic power factor correction.
What is the power factor formula for three phase?
For a balanced three-phase load, PF = W / (1.732 x V x A), with line-to-line volts. A load drawing 11,000 watts at 400 volts and 20 amps has 13.856 kVA and a power factor of 0.794. Mixing line-to-neutral volts into this formula gives a wrong answer.
What is the power factor formula for single phase?
For single-phase, PF = W / (V x A). A device that draws 15 amps at 120 volts and 1,500 watts has an apparent power of 1.8 kVA and a power factor of 0.833. A pure heater at 1,800 watts on the same 15 amps would be 1.000, which is unity.
How do I find power factor from kW and kVAR?
Combine them with the power triangle: kVA = √(kW squared + kVAR squared), then PF = kW / kVA. For 150 kW and 100 kVAR, kVA is 180.28 and PF is 0.832. The phase angle is 33.69 degrees. This is the kW and kVAR mode of the calculator.
How do I get power factor from the phase angle?
Take the cosine of the angle between voltage and current. A 25 degree angle gives 0.9063, and a 36.87 degree angle gives 0.8. At 0 degrees the power factor is 1, and at 90 degrees it is 0. Use the angle mode of the calculator with a value from 0 to 90 degrees.
What is a good power factor?
Closer to 1 is better. Many utilities and facilities aim for 0.90 to 0.95 or higher, and some tariffs add charges when the power factor falls below a set level. Check your own tariff for the threshold, since it varies by utility and country. A value of 0.95 is a common correction target.
How many kVAR do I need to correct power factor?
Use kVAR = kW x (tan(acos PF1) - tan(acos PF2)). Raising 100 kW from 0.80 to 0.95 needs 42.1 kVAR. Raising it from 0.70 to 0.95 needs 69.2 kVAR. The multiplier table gives the factor per kW for common cases.
What is leading and lagging power factor?
A lagging power factor means current is behind voltage, which is typical of induction motors and transformers. A leading power factor means current is ahead of voltage, which happens with capacitive loads and over-corrected systems. The magnitude is the same cosine value, so this calculator treats reactive power as a size.
Why does a low power factor matter?
A low power factor means more current for the same kW. At 0.7 a load draws 43 percent more current than at 1. That loads cables, transformers and generators, adds losses and may attract utility charges. Raising 100 kW from 0.70 to 0.95 cuts the current by 26.3 percent.
What is the power factor of a resistive load?
It is 1, or unity, because voltage and current are in step. Heaters, kettles, ovens and incandescent lamps behave this way. Motors, transformers and fluorescent ballasts have lower values, and electronic loads can have a low power factor because the current is distorted rather than shifted.
What is the power triangle?
It is a right triangle with real power kW along the base, reactive power kVAR as the height and apparent power kVA as the longest side. The angle between kW and kVA is the phase angle, and its cosine is the power factor. For 80 kW and 60 kVAR the hypotenuse is 100 kVA and the PF is 0.8.
Can power factor be more than 1?
No. Real power can never exceed apparent power, so the power factor lies between 0 and 1. If your numbers give a result above 1, the readings were taken at different times, the units are mixed up or the three-phase factor of 1.732 was left out. The calculator reports an error in that case.
How do I use this power factor calculator?
Choose how you want to calculate: from kW and kVA, from kW and kVAR, from watts, volts and amps, from a phase angle, or to find the capacitor kVAR needed to reach a target. Fill in the boxes that appear, and the results show power factor, angle, kVA, kVAR and, in correction mode, the capacitor size and number of stages.
Is there a power factor calculator app?
You do not need to install anything. This page works in any phone or desktop browser, and you can add it to your home screen if you want quick access. Enter the numbers, read the results and, if you like, copy them for your notes or a spreadsheet.
Is this an IPSC or pistol power factor calculator?
No. This page covers electrical power factor. The shooting sports figure is a different quantity, the bullet's momentum, calculated as bullet weight times velocity, commonly in grains times feet per second divided by 1,000. It has no connection to volts, amps or kVA.
How much does correction reduce the current?
The current falls in the ratio PF1 / PF2 at the same kW and voltage. Raising a load from 0.75 to 0.95 cuts the current by 21.1 percent. The same 500 kW needs 526 kVA instead of 667 kVA, which frees capacity in the transformer and cables.
Can I use this to size a capacitor bank?
Use it for planning only. A real capacitor bank depends on the voltage, harmonics, switching, the load profile and the rules for your installation. Follow the National Electrical Code and local code, and have a qualified electrician or engineer specify and install the equipment. Capacitors store energy and can be dangerous.
Does the calculator work for three phase?
Yes, in the watts, volts and amps mode choose three-phase with line-to-line voltage. The kW, kVA and kVAR modes already apply to any balanced supply, because they use total power. The capacitor calculation uses the total three-phase kW and gives the total kVAR for the bank.
References
- [1] Wikipedia contributors. “Power factor.” Wikipedia. Accessed 2026-10-07.
- [2] Wikipedia contributors. “AC power.” Wikipedia. Accessed 2026-10-07.
- [3] Wikipedia contributors. “Reactive power.” Wikipedia. Accessed 2026-10-07.
- [4] Wikipedia contributors. “Three-phase electric power.” Wikipedia. Accessed 2026-10-07.
- [5] Wikipedia contributors. “Power factor (shooting sports).” Wikipedia. Accessed 2026-10-07.
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