Change the Subject of a Formula
Rearrange any formula, like v = u + at, to make a different letter the subject.
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How to use this calculator
Type your formula with an equals sign, then choose which letter you want on its own. The rearranged formula and every step appear immediately.
How it's calculated
To change the subject, do the same operation to both sides until your chosen letter is alone. When the letter appears squared, the quadratic formula or a square root is used.
Worked example
v = u + at, make t the subject. Subtract u from both sides: v − u = at. Divide both sides by a: t = (v − u) / a.
Frequently asked questions
Can I use any letters?
Yes. Use single letters. Letters next to each other multiply, so at means a × t. Use brackets for fractions, like (a+b)/c.
What if the letter is squared?
The calculator gives the ± square-root form, for example r = ±√(A / π).
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Last updated October 2026. Results are for learning and guidance; always check important work. Calculations run in your browser and are not stored.