Rearrange Formula Calculator
Pick a formula, choose the variable you want to make the subject, then enter the known values.
What Is a Rearrange Formula Calculator?
A rearrange formula calculator helps you isolate one variable in an equation and compute its value from the variables you already know. Instead of manually transposing terms each time, you pick the target variable and let the tool do the algebraic setup instantly. This is useful in physics, finance, engineering, and everyday problem solving.
For example, if you know force and acceleration and need mass, you start with F = m × a and rearrange to m = F ÷ a. The calculator handles this rearrangement logic and then performs the numeric calculation.
Formulas Available in This Calculator
- Distance-speed-time: d = v × t
- Force-mass-acceleration: F = m × a
- Ohm’s law: V = I × R
- Rectangle area: A = l × w
- Circle area: A = πr²
- Density: ρ = m ÷ V
- Simple interest: I = P × r × t (use decimal rate, e.g., 0.08 for 8%)
How to Rearrange Formulas Manually
1) Identify the target variable
Decide which symbol you need to solve for. Treat every other variable as known.
2) Undo operations in reverse order
If a term is multiplied, divide both sides. If something is added, subtract both sides. Always do the same operation on both sides to keep the equation balanced.
3) Simplify and substitute values
Once your target variable stands alone, plug in numbers and calculate. Watch units and denominator values carefully.
Worked Examples
Example 1: Solve for speed
Given d = 150 and t = 3, using d = v × t: rearrange to v = d ÷ t, then v = 150 ÷ 3 = 50.
Example 2: Solve for resistance
Given V = 12 and I = 2, using V = I × R: rearrange to R = V ÷ I, so R = 6.
Example 3: Solve for radius from area
Given A = 78.54, using A = πr²: rearrange to r = √(A ÷ π), so r ≈ 5.
Common Mistakes to Avoid
- Dividing by zero (for example, time = 0 in v = d/t).
- Using interest rate percent as a whole number instead of decimal.
- Mixing units (meters with kilometers, hours with seconds, etc.).
- Forgetting that square root outputs the principal (positive) value in this context.
Why This Tool Helps
This calculator speeds up repeated algebra tasks, reduces transposition errors, and gives immediate feedback. It is especially useful for students checking homework, professionals doing quick field calculations, and anyone reviewing core formula skills.