Sizu Home › Calculators › Rearrange a Formula
Opens on Chapter 10’s example: a 1,500-watt heater on 120 volts: how many amps?
Enter your numbers, then press Work it out.
How it works
Treat the letter you want as the unknown and every other letter as a number you don’t know yet. Undo what’s been done to your letter, in reverse order, doing the same to both sides: take away what’s added, then divide by what multiplies it. The page shows each move on the letters, then puts your numbers in, and checks by working the original formula forward with the answer.
From the book, Chapter 10. I = P ÷ V gives 12.5 amps; t = d ÷ r gives 2.5 hours; 68°F is 20°C; a 50 ft perimeter with 15 ft sides leaves widths of 10 ft; $60 buys 120 sheets and $100 buys 220; $90 interest on $1,500 over 2 years is a rate of 3%; 12 volts and 0.5 amps means 24 ohms; a 30 sq in triangle on a 12 in base is 5 in tall. Every chapter and its calculator →
Arithmetic only: this shows how a formula is rearranged, not electrical, engineering or financial advice. Numbers can be typed as 1,500, $60, 0.5 or 3%. Everything stays in your browser: no sign-up, nothing stored or sent.