Amps to kilowatts and back: table & calculator
16 A is 3.68 kW on a single-phase 230 V supply and 11.09 kW on a three-phase 400 V supply (cos φ = 1). Below: a 6–63 A table; the calculator also works backwards, from kW to amps, with breaker and cable size.
Parameters
Result (1ph 230V)
Recommendations
Reference: kW → A (230V, cos φ 0.95)
How many kW in amps: 6–63 A table
Single-phase: P = U × I × cos φ. Three-phase: P = √3 × U × I × cos φ. Nominal low-voltage supply: 230/400 V (IEC 60038). cos φ = 1 for heaters and incandescent lamps; 0.95 is typical for household appliances.
| Current, A | 1-phase, 230 V, cos φ 1.00, kW | 1-phase, 230 V, cos φ 0.95, kW | 3-phase, 400 V, cos φ 1.00, kW | 3-phase, 400 V, cos φ 0.95, kW |
|---|---|---|---|---|
| 6 A | 1.38 | 1.31 | 4.16 | 3.95 |
| 10 A | 2.30 | 2.19 | 6.93 | 6.58 |
| 16 A | 3.68 | 3.50 | 11.09 | 10.53 |
| 20 A | 4.60 | 4.37 | 13.86 | 13.16 |
| 25 A | 5.75 | 5.46 | 17.32 | 16.45 |
| 32 A | 7.36 | 6.99 | 22.17 | 21.06 |
| 40 A | 9.20 | 8.74 | 27.71 | 26.33 |
| 50 A | 11.50 | 10.93 | 34.64 | 32.91 |
| 63 A | 14.49 | 13.77 | 43.65 | 41.47 |
Calculation formula: Watts → Amps
How to convert watts to amps?
For single-phase network 230V: I (A) = P (W) / (230 × cos φ). At cos φ = 1.0 (heaters, heating elements): 1 kW = 4.35 A. At cos φ = 0.95 (household appliances): 1 kW = 4.58 A. At cos φ = 0.8 (motors): 1 kW = 5.43 A.
For three-phase network 400V: I = P / (√3 × 400 × cos φ) = P / (693 × cos φ). At cos φ = 0.85: 10 kW = 17.0 A per phase. The current of a three-phase load is almost three times less than that of a single-phase load at the same power.
After calculating the current, select a circuit breaker from the standard range (for example 6, 10, 16, 20, 25, 32, 40 A) with a rating of at least 110% of the calculated current. Size the cable for that breaker rating, not for the calculated current: the cable has to carry the current the breaker is rated for. On a three-phase network the cable is sized for three loaded conductors. The calculator assumes a copper cable with PVC insulation laid in conduit.
For three-phase circuits, it is important to distribute the load evenly across phases. If you have calculated the current for a three-phase device (e.g., a 10 kW motor = 17.0 A per phase), check the phase balance in the phase balance calculator — the imbalance should not exceed 15–20% according to IEC 60364.
To select a cable based on the calculated current, use the cable cross-section calculator — it takes into account line length, material, installation method, and permissible voltage drop.
Watts, volt-amperes, and kilowatts — what is the difference?
Watt (W) is active power that performs useful work: heating, rotation, lighting. Volt-ampere (VA) is apparent power consumed by the device from the grid, including reactive component. For heaters and lamps, W = VA (cos φ = 1). For motors and compressors, VA > W.
| Device | Power, W | cos φ | Apparent power, VA | Current, A (230V) |
|---|---|---|---|---|
| Kettle 2 kW | 2 000 | 1.00 | 2 000 VA (2 kVA) | 8.7 |
| Boiler 2 kW | 2 000 | 1.00 | 2 000 VA (2 kVA) | 8.7 |
| Air conditioner 2.5 kW | 2 500 | 0.85 | 2 941 VA (2.9 kVA) | 12.8 |
| Washing machine 2 kW | 2 000 | 0.85 | 2 353 VA (2.4 kVA) | 10.2 |
| Motor 5.5 kW | 5 500 | 0.82 | 6 707 VA (6.7 kVA) | 29.2 |
| Welding machine 5 kW | 5 000 | 0.70 | 7 143 VA (7.1 kVA) | 31.1 |
UPS (uninterruptible power supply) and generators specify power in VA. To determine how many watts they can handle, multiply VA by the load's cos φ (typically 0.6–0.8 for office equipment).
Frequently asked questions
How many kW is 16 amps?
On a single-phase 230 V supply at cos φ = 1: 16 A × 230 V = 3.68 kW; at cos φ = 0.95 it is 3.5 kW. On a three-phase 400 V supply at cos φ = 1: 16 A × √3 × 400 V = 11.09 kW. Formulas: P = U × I × cos φ (1-phase) and P = √3 × U × I × cos φ (3-phase). For other currents (6, 10, 20, 25, 32, 40, 50, 63 A) see the table on this page.
How many amps in 1 kilowatt at 230V?
At 230V and cos φ = 1.0: 1 kW = 4.35 A. At cos φ = 0.95 (typical for household appliances): 1 kW = 4.58 A. Formula: I = P / (U × cos φ). For three-phase network 400V: 1 kW = 1.44 A (cos φ = 1.0).
How to calculate current for a three-phase network?
For three-phase network: I = P / (√3 × U × cos φ), where U is line voltage (400V). Example: electric motor 10 kW, cos φ = 0.85: I = 10000 / (1.732 × 400 × 0.85) = 17.0 A. This is the current on each phase.
What is cos φ and why consider it?
Cos φ (power factor) indicates what fraction of apparent power is active (useful). For resistive loads (heaters, incandescent lamps) cos φ = 1.0. For motors, compressors, transformers — 0.7–0.9. A low cos φ leads to increased current for the same active power.
Why is starting current higher than operating current?
When starting an electric motor, the rotor is stationary and does not generate back-EMF, so the current is limited only by the active resistance of the windings. Starting current is 3–7 times the rated current. For MCB selection, use the operating current, but choose characteristic C or D to avoid tripping during start.
Which MCB to install for a known power?
Calculate the operating current (I = P / (U × cos φ)), then select the nearest standard MCB rating above: 6, 10, 16, 20, 25, 32, 40, 50, 63 A. The MCB rating must not exceed the cable's permissible current. For motors, characteristic C or D.
How to convert kW to kVA and vice versa?
kVA = kW / cos φ. Example: air conditioner 2.5 kW with cos φ = 0.85: 2.5 / 0.85 = 2.94 kVA. Reverse: kW = kVA × cos φ. For heaters and heating elements cos φ = 1.0, so kW = kVA.
How many watts in one volt-ampere?
W = VA × cos φ. At cos φ = 1.0 (heaters): 1 VA = 1 W. At cos φ = 0.85 (motors, air conditioners): 1 VA = 0.85 W. Volt-ampere (VA) is the unit of apparent power, watt (W) is active power.
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