Ohm's Law and Watt's Law Tables (Volts, Amps, Ohms, Watts)
Know any two of volts, amps, ohms and watts and the other two follow. The tables below work every pairing, with the same arithmetic and rounding as the Equipment Tracker app. No account, nothing to install.
REFERENCE TOOL — NOT A GUARANTEE
This tool does the math for you, but it is not a substitute for your own professional judgment, code compliance check, or manufacturer specifications. Always verify results before doing any work — you are responsible for your own calculations.
Ohm's & Watt's Law Calculator (Solve Any Field)
Enter any 2 known values to solve for the rest. Each table below gives two values and solves the other two.
Given volts and amps
| Volts (V) given | Amps (I) given | Ohms (R) | Watts (P) |
|---|---|---|---|
| 12 | 1 | 12.00 | 12.0 |
| 12 | 5 | 2.40 | 60.0 |
| 12 | 10 | 1.20 | 120.0 |
| 12 | 20 | 0.60 | 240.0 |
| 24 | 1 | 24.00 | 24.0 |
| 24 | 5 | 4.80 | 120.0 |
| 24 | 10 | 2.40 | 240.0 |
| 24 | 20 | 1.20 | 480.0 |
| 120 | 1 | 120.00 | 120.0 |
| 120 | 5 | 24.00 | 600.0 |
| 120 | 10 | 12.00 | 1200.0 |
| 120 | 20 | 6.00 | 2400.0 |
| 240 | 1 | 240.00 | 240.0 |
| 240 | 5 | 48.00 | 1200.0 |
| 240 | 10 | 24.00 | 2400.0 |
| 240 | 20 | 12.00 | 4800.0 |
Given volts and ohms
| Volts (V) given | Amps (I) | Ohms (R) given | Watts (P) |
|---|---|---|---|
| 12 | 2.40 | 5 | 28.8 |
| 12 | 1.20 | 10 | 14.4 |
| 12 | 0.50 | 24 | 6.0 |
| 12 | 0.12 | 100 | 1.4 |
| 24 | 4.80 | 5 | 115.2 |
| 24 | 2.40 | 10 | 57.6 |
| 24 | 1.00 | 24 | 24.0 |
| 24 | 0.24 | 100 | 5.8 |
| 120 | 24.00 | 5 | 2880.0 |
| 120 | 12.00 | 10 | 1440.0 |
| 120 | 5.00 | 24 | 600.0 |
| 120 | 1.20 | 100 | 144.0 |
| 240 | 48.00 | 5 | 11520.0 |
| 240 | 24.00 | 10 | 5760.0 |
| 240 | 10.00 | 24 | 2400.0 |
| 240 | 2.40 | 100 | 576.0 |
Given volts and watts
| Volts (V) given | Amps (I) | Ohms (R) | Watts (P) given |
|---|---|---|---|
| 12 | 8.33 | 1.44 | 100 |
| 12 | 41.67 | 0.29 | 500 |
| 12 | 83.33 | 0.14 | 1000 |
| 12 | 200.00 | 0.06 | 2400 |
| 24 | 4.17 | 5.76 | 100 |
| 24 | 20.83 | 1.15 | 500 |
| 24 | 41.67 | 0.58 | 1000 |
| 24 | 100.00 | 0.24 | 2400 |
| 120 | 0.83 | 144.00 | 100 |
| 120 | 4.17 | 28.80 | 500 |
| 120 | 8.33 | 14.40 | 1000 |
| 120 | 20.00 | 6.00 | 2400 |
| 240 | 0.42 | 576.00 | 100 |
| 240 | 2.08 | 115.20 | 500 |
| 240 | 4.17 | 57.60 | 1000 |
| 240 | 10.00 | 24.00 | 2400 |
Given amps and ohms
| Volts (V) | Amps (I) given | Ohms (R) given | Watts (P) |
|---|---|---|---|
| 5.0 | 1 | 5 | 5.0 |
| 10.0 | 1 | 10 | 10.0 |
| 24.0 | 1 | 24 | 24.0 |
| 100.0 | 1 | 100 | 100.0 |
| 25.0 | 5 | 5 | 125.0 |
| 50.0 | 5 | 10 | 250.0 |
| 120.0 | 5 | 24 | 600.0 |
| 500.0 | 5 | 100 | 2500.0 |
| 50.0 | 10 | 5 | 500.0 |
| 100.0 | 10 | 10 | 1000.0 |
| 240.0 | 10 | 24 | 2400.0 |
| 1000.0 | 10 | 100 | 10000.0 |
| 100.0 | 20 | 5 | 2000.0 |
| 200.0 | 20 | 10 | 4000.0 |
| 480.0 | 20 | 24 | 9600.0 |
| 2000.0 | 20 | 100 | 40000.0 |
Given amps and watts
| Volts (V) | Amps (I) given | Ohms (R) | Watts (P) given |
|---|---|---|---|
| 100.0 | 1 | 100.00 | 100 |
| 500.0 | 1 | 500.00 | 500 |
| 1000.0 | 1 | 1000.00 | 1000 |
| 2400.0 | 1 | 2400.00 | 2400 |
| 20.0 | 5 | 4.00 | 100 |
| 100.0 | 5 | 20.00 | 500 |
| 200.0 | 5 | 40.00 | 1000 |
| 480.0 | 5 | 96.00 | 2400 |
| 10.0 | 10 | 1.00 | 100 |
| 50.0 | 10 | 5.00 | 500 |
| 100.0 | 10 | 10.00 | 1000 |
| 240.0 | 10 | 24.00 | 2400 |
| 5.0 | 20 | 0.25 | 100 |
| 25.0 | 20 | 1.25 | 500 |
| 50.0 | 20 | 2.50 | 1000 |
| 120.0 | 20 | 6.00 | 2400 |
Given ohms and watts
| Volts (V) | Amps (I) | Ohms (R) given | Watts (P) given |
|---|---|---|---|
| 22.4 | 4.47 | 5 | 100 |
| 50.0 | 10.00 | 5 | 500 |
| 70.7 | 14.14 | 5 | 1000 |
| 109.5 | 21.91 | 5 | 2400 |
| 31.6 | 3.16 | 10 | 100 |
| 70.7 | 7.07 | 10 | 500 |
| 100.0 | 10.00 | 10 | 1000 |
| 154.9 | 15.49 | 10 | 2400 |
| 49.0 | 2.04 | 24 | 100 |
| 109.5 | 4.56 | 24 | 500 |
| 154.9 | 6.45 | 24 | 1000 |
| 240.0 | 10.00 | 24 | 2400 |
| 100.0 | 1.00 | 100 | 100 |
| 223.6 | 2.24 | 100 | 500 |
| 316.2 | 3.16 | 100 | 1000 |
| 489.9 | 4.90 | 100 | 2400 |
Frequently asked questions
How do I calculate watts from volts and amps?
Multiply volts by amps. In the Equipment Tracker app's calculator, 120 volts and 10 amps give 1200.0 watts.
How do I find resistance from volts and amps?
Divide volts by amps. With 120 volts and 10 amps the app's calculator gives 12.00 ohms.
What if I know the watts and the ohms but not the voltage?
The app takes the square root of watts times ohms. 100 watts across 5 ohms is 22.4 volts, and the app shows 4.47 amps for it.
What if I enter more than two values?
The app solves from the first pair it finds in this order: volts and amps, volts and ohms, volts and watts, amps and ohms, amps and watts, ohms and watts. The tables on this page give exactly two values, so there is no ambiguity.
How are the results rounded?
A solved value is shown to two decimals for amps and ohms and to one decimal for volts and watts, the way the app shows it. A value you entered is shown as you entered it.
Does this cover three-phase power, power factor or AC impedance?
No. The Equipment Tracker app's calculator solves volts, amps, ohms and watts from any two of them and nothing else, so that is all this page shows.
Does this page store anything or need an account?
No to both. It does the math for you, but it is not a substitute for your own professional judgment, a code compliance check or the manufacturer's specifications.
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