Volts, amps, and watts
What you'll learn
Read any circuit in the three numbers that define it — and the one formula that ties them together.
Every electrical question starts with three numbers: volts, amps, and watts. Get how they relate and the rest of the work stops feeling like magic.
The water analogy
- Volts are pressure — how hard the electricity is pushed. A home runs on 120 V, with 240 V for big appliances.
- Amps are flow — how much electricity actually moves.
- Watts are power — the work being done. Watts is what you pay for, and what heats up a wire.
The one formula
Watts = volts × amps
That's the whole thing. Rearranged, it answers the question you actually ask on the job:
Amps = watts ÷ volts
A 1,500 W space heater on a 120 V circuit draws:
1,500 ÷ 120 = 12.5 amps
Why this is the whole game
Wire and breakers are rated in amps. Appliances are labeled in watts. This formula is the bridge — it turns the number on the label into the number that decides your wire and breaker. Every electrical calculator starts here; now you can do it in your head.
Check your understanding
Question 1 of 2
A 1,500 W heater runs on a 120 V circuit. How many amps does it draw?