To use the calculator, select the current type, enter the power in watts and voltage in volts, and provide the power factor (a value between 0 and 1) for AC systems. For AC three phase systems, choose between line to line or line to neutral voltage. Click the “Calculate” button to display the current in amps and milliamps in the output section. Click “Reset” to clear all fields and start fresh.
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DC Watts to Amps Calculation
I(A) = P(W) / V(V), where
I(A) – electric current in amperes (A),
P(W) – power P in watts (W),
V(V) – voltage V in volts (V).
Example
If P = 600W, V = 120V, then
I(A) = 600W / 120V = 5A
Conversion for Single-Phase AC Circuits
I(A) = P(W) / PF * V(V), where
I(A) – phase current in amperes (A),
P(W) – power P in watts (W),
PF – power factor,
V(V) – voltage V in volts (V).
Example
If P = 1000W, V = 120V, PF = 0,8, then
I(A) = 1000W / (0.8 × 230V) = 5.4347 A
AC Three Phase Watts to Amps Calculation
Calculation with Line-to-Line Voltage
I(A) = P(W)√3 × PF × VL-L(V), where
I(A) – phase current in amperes (A),
P(W) – power P in watts (W),
PF – power factor,
VL-L(V) – line to line RMS voltage in volts (V).
Calculation with Line to Neutral Voltage
For three-phase AC circuits where the line to neutral voltage is known, the formula to convert watts to amps is:
I(A) = P(W)3 × PF × VL-N(V), where
I(A) – phase current in amperes (A),
P(W) – power P in watts (W),
PF – power factor,
VL-N(V) – line to neutral RMS voltage in volts (V).
Typical Power Factor Values
Here are typical power factor values in the table:
| Device/Load | Power Factor |
|---|---|
| Incandescent lamps | 1.0 |
| Resistive loads | 1.0 |
| Synchronous motors | 0.8-0.95 |
| Induction motors (small) | 0.7-0.8 |
| Induction motors (large) | 0.85-0.95 |
| Transformers | 0.8-0.95 |
| Fluorescent lighting (magnetic ballast) | 0.7-0.9 |
| Fluorescent lighting (electronic ballast) | 0.9-0.99 |
| Computers and electronics | 0.6-0.8 |
Watts to Amps Table (12V DC)
| Watts | Amps |
|---|---|
| 5 | 0.417 |
| 10 | 0.833 |
| 20 | 1.667 |
| 30 | 2.500 |
| 40 | 3.333 |
| 50 | 4.167 |
| 60 | 5.000 |
| 70 | 5.833 |
| 80 | 6.667 |
| 90 | 7.500 |
| 100 | 8.333 |
| 200 | 16.667 |
| 300 | 25.000 |
| 400 | 33.333 |
| 500 | 41.667 |
Watts to Amps Table (120V Single-Phase AC)
| Watts | Amps |
|---|---|
| 10 | 0.083 |
| 20 | 0.167 |
| 30 | 0.250 |
| 40 | 0.333 |
| 50 | 0.417 |
| 60 | 0.500 |
| 70 | 0.583 |
| 80 | 0.667 |
| 90 | 0.750 |
| 100 | 0.833 |
| 200 | 1.667 |
| 300 | 2.500 |
| 400 | 3.333 |
| 500 | 4.167 |
| 600 | 5.000 |
| 700 | 5.833 |
| 800 | 6.667 |
| 900 | 7.500 |
| 1000 | 8.333 |
Watts to Amps Table (240V Single-Phase AC)
| Watts | Amps |
|---|---|
| 10 | 0.042 |
| 20 | 0.083 |
| 30 | 0.125 |
| 40 | 0.167 |
| 50 | 0.208 |
| 60 | 0.250 |
| 70 | 0.292 |
| 80 | 0.333 |
| 90 | 0.375 |
| 100 | 0.417 |
| 200 | 0.833 |
| 300 | 1.250 |
| 400 | 1.667 |
| 500 | 2.083 |
| 600 | 2.500 |
| 700 | 2.917 |
| 800 | 3.333 |
| 900 | 3.750 |
| 1000 | 4.167 |
| 1500 | 6.250 |
| 2000 | 8.333 |
