Current Draw Calculator
Work out the current an appliance draws and whether the circuit can support it.
About Current Draw Calculator
Current is power divided by voltage and power factor. Continuous loads are conventionally limited to 80 per cent of the breaker rating, because thermal-magnetic breakers are not designed to sit at their nameplate current indefinitely. Adding a second high-power appliance to a circuit already at 70 per cent is the most common cause of nuisance tripping.
Formula
Current Draw
I = P ÷ (V × power factor)
- 80% rule
- Continuous loads are normally limited to 80% of breaker rating
Worked example
With the default values below, Current Draw Calculator returns Current Drawn of 10.435. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Appliance powerminimum 0 W
- 2,400 W
- Supply voltageminimum 1 V
- 230 V
- Power factoraccepts 0.01–1
- 1
- Circuit breaker ratingminimum 1 A
- 16 A
Results
- Current Drawn
- 10.435 A
- Share of Circuit Capacity Used
- 65.2%
- Spare Capacity
- 5.565 A
- Maximum Power the Circuit Supports
- 3,680.0 W
- Verdict
- Within safe loading
Step by step
- 1Values used
- 2Current Draw
- 3Current Drawn= 10.435 A
- 4Share of Circuit Capacity Used= 65.2
- 5Spare Capacity= 5.565 A
- 6Maximum Power the Circuit Supports= 3,680.0 W
- 7Verdict= Within safe loading
Assumptions and limits
- The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
How is Current Draw calculated?
I = P ÷ (V × power factor) Current is power divided by voltage and power factor. Continuous loads are conventionally limited to 80 per cent of the breaker rating, because thermal-magnetic breakers are not designed to sit at their nameplate current indefinitely.
Why does Current Draw matter?
Adding a second high-power appliance to a circuit already at 70 per cent is the most common cause of nuisance tripping.
What values do I need to enter?
This calculator takes 4 inputs: Appliance power, Supply voltage, Power factor, Circuit breaker rating. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.