- What's the formula to convert kW to amps?
- It depends on the current type. DC: I = (kW × 1000) ÷ V. AC single-phase: I = (kW × 1000) ÷ (PF × V). AC three-phase line-to-line: I = (kW × 1000) ÷ (√3 × PF × V_LL), where √3 ≈ 1.732. AC three-phase line-to-neutral: I = (kW × 1000) ÷ (3 × PF × V_LN). The × 1000 converts kilowatts to watts; dividing by volts gives amperes. The power factor appears in every AC formula and in none of the DC ones.
- Why does power factor appear here but not in the kVA to amps calculator?
- Because kW and kVA measure different things. kVA is apparent power — volts times amps — so it already contains whatever the power factor is doing, and dividing by it again would be counting the same correction twice. kW is real power, the portion actually converted into work, heat, or motion. To get back to the current in the wire you have to divide the real power by the power factor. This is the single most common mistake in the whole kW/kVA family: if you type a kVA nameplate into a kW field and also set PF to 0.8, your answer is 25% too high.
- What power factor should I use if I don't know it?
- 0.8 is the conventional planning default and is deliberately pessimistic — it over-estimates current slightly, which is the safe direction when you're sizing a conductor. If you can do better, use the actual figure: pure resistive loads (electric heaters, incandescent lamps, kettles, resistance ovens) are 1.0; modern LED drivers and switch-mode power supplies with active PFC run 0.95 or better; induction motors are roughly 0.85 at full load but sag badly to 0.5 or lower when lightly loaded; welders and older fluorescent ballasts can sit near 0.6. Motor nameplates usually print the figure. When the number matters for a purchase or a permit, measure it rather than assume.
- Is 10 kW the same current on single-phase and three-phase?
- No, and the difference is large. 10 kW at 240 V single-phase with PF 0.8 draws 52.08 A. The same 10 kW at 240 V three-phase line-to-line with the same power factor draws 30.07 A — about 58% of the single-phase figure, because the √3 factor in the three-phase formula spreads the load across three conductors. That's the entire practical reason three-phase exists for larger loads: same power, less current per conductor, so thinner and cheaper copper.
- Line-to-line or line-to-neutral — which voltage do I enter?
- Nearly always line-to-line. In North America, 208, 240, 277 and 480 V quoted on a three-phase nameplate are line-to-line figures; in most of Europe, 400 V is. Line-to-neutral is the voltage from one phase conductor to neutral — 120 V on a 208 V system, 230 V on a 400 V system, 277 V on a 480 V system. The relationship is V_LL = √3 × V_LN. If your spec only gives one three-phase voltage and doesn't say which it is, it's line-to-line. Picking the wrong one puts your answer off by a factor of √3, about 73%.
- Can I use this to size a breaker?
- It gives you step one, not the final answer. Under the NEC (US), a continuous load is sized at 125% of the calculated current (NEC 210.20 / 215.2), so a computed 52 A typically lands on a 70 A breaker after rounding up to the next standard size. From there, conductor ampacity has to match the breaker, and then ambient-temperature correction, conduit-fill de-rating, and the terminal temperature rating all apply. Motors have their own rules entirely and are sized from the NEC full-load-current tables rather than from a calculation like this one. Use this number to sanity-check a design or an invoice, not to skip the code steps.
- What does the kVA figure underneath the result mean?
- It's the apparent power — kW divided by the power factor — and it's what generators, UPS units, and transformers are rated in. A 10 kW load at 0.8 power factor is 12.5 kVA, so a 10 kVA generator will not run it even though the wattage looks like it should fit. The number only appears when the power factor isn't 1, because at unity the two figures are identical and showing both would just be noise.
- Why does the result switch to scientific notation for huge numbers?
- Readability on a phone. Past a million amps the plain digits stop fitting on a narrow screen and start pushing the layout sideways, so the display switches to a compact form like 1.000E9. You'll only see this with deliberately extreme inputs — a real circuit at these currents doesn't exist outside a fusion lab or a short-circuit study. Everything below a million amps renders as ordinary grouped digits.
- How accurate is four significant figures?
- More precise than the inputs deserve. Grid voltage legally varies by around ±5%, motor power factor shifts with load, and nameplate ratings are themselves rounded. Reporting 52.08 A instead of 52.083333 A tracks the real precision of what you typed. If you need a number for a submittal, use the measured voltage and the measured power factor rather than more decimal places on an assumed one.
- Does anything I type get sent to a server?
- No. The whole calculation runs in your browser. There's no account, no project to save, no quote form, and no analytics event carrying your kW or voltage anywhere. The page is static and the widget is a small React component doing arithmetic locally. Refresh the page and your inputs are gone — nothing is written to storage either. A unit conversion shouldn't require a privacy policy.
