Formulas for mathematics, physics and chemistry, each one explained properly and each one with a calculator that shows its working. Put your own numbers in and you get the full solution line by line — the rearrangement, the substitution, the arithmetic — not just an answer.
Most formula calculators give you a number and leave you no wiser. That is fine if you already understand the method and are checking arithmetic, and useless if you are trying to learn it. Every calculator here writes out the steps the way a teacher would on a board, and says why each move is being made.
You can also leave any box empty and it will solve for that one instead. Finding acceleration from a force, or the first term of a sequence from its sum, is the same equation read backwards — so the pages handle it rather than making you rearrange first.
Everything runs inside your own browser. Nothing you type is uploaded, nothing is stored, and there is no account to create. The pages work on a phone.
Mathematics
Algebra and geometry, with the rearrangements written out rather than assumed.
- Pythagoras’ theorema² + b² = c²Find any side of a right-angled triangle from the other two.Grades 9–10
- The quadratic formulax = (−b ± √(b² − 4ac)) ⁄ 2aSolve any equation of the form ax² + bx + c = 0.Grades 9–10
- Arithmetic progressionaₙ = a + (n − 1)d, Sₙ = n⁄2 (a + aₙ)Any term, or the sum of a run of terms, in a sequence that steps by a fixed amount.Grades 11–12
Physics
Forces and motion, with units carried through every line of the working.
- Newton’s second lawF = maThe force needed to accelerate a mass, and what that force produces.Grades 9–10
- The equations of motionv = u + at, s = ut + ½at², v² = u² + 2asGive any three of u, v, a, s and t; the other two follow.Grades 9–12
- Projectile motionR = u² sin 2θ ⁄ g, H = u² sin²θ ⁄ 2g, T = 2u sin θ ⁄ gRange, greatest height and time of flight for something launched at an angle.Grades 11–12
Chemistry
Moles, solutions and gases, with the unit cancellation shown rather than skipped.
- Moles, mass and molar massn = m ⁄ MConvert between the mass you can weigh and the number of particles you actually need.Grades 9–10
- The dilution formulaC₁V₁ = C₂V₂Work out what to mix when you make a weaker solution from a stronger one.Grades 9–12
- The ideal gas lawPV = nRTTies pressure, volume, amount and temperature of a gas into one equation.Grades 11–12