Science & Engineering Calculators
Mechanics, energy, circuits and solutions — with the idealisation each formula rests on stated rather than hidden. All 30 are free and run in your browser. Each one shows the formula behind the result.
Speed Distance Time Calculator
Any one of the three from the other two, in four units.
OpenVelocity Calculator
Final velocity under constant acceleration, with the distance.
OpenAcceleration Calculator
Acceleration in m/s² and in g, which is the legible one.
OpenFree Fall Calculator
Fall speed and time, with the air resistance caveat stated.
OpenProjectile Motion Calculator
Range, height and flight time, and why 45° is optimal.
OpenForce Calculator
F = ma, in newtons, kilograms-force and pounds-force.
OpenKinetic Energy Calculator
½mv², and why doubling speed quadruples the damage.
OpenPotential Energy Calculator
mgh, and how little food energy lifting actually costs.
OpenWork Calculator
W = Fd cos θ, including the case that comes out zero.
OpenPower Calculator
Watts, kilowatts and horsepower, with a running cost.
OpenMomentum Calculator
Momentum, impulse, and the principle behind crumple zones.
OpenTorque Calculator
Turning force, in newton-metres and pound-feet.
OpenDensity Calculator
Density, mass or volume, and whether it floats.
OpenPressure Calculator
From a force on an area, or from a depth of fluid.
OpenResistor Calculator
Series and parallel totals for up to four resistors.
OpenCapacitor Calculator
Series and parallel, which are the reverse of resistors.
OpenVoltage Divider Calculator
Output voltage, current and the power each resistor dissipates.
OpenLED Resistor Calculator
The series resistor, rounded up to a standard value.
OpenBattery Life Calculator
Runtime with a derating factor, because the ideal figure never happens.
OpenTransformer Calculator
Turns ratio, secondary voltage and current, with power conserved.
OpenRC Time Constant Calculator
τ = RC, with the charging percentages and the filter cutoff.
OpenInductance Calculator
Reactance at frequency, and where L and C cancel.
OpenPower Factor Calculator
Real against apparent power, and the current it costs.
OpenMolarity Calculator
Moles per litre of solution — not of solvent.
OpenDilution Calculator
M₁V₁ = M₂V₂, with the diluent volume you actually need.
OpenIdeal Gas Law Calculator
PV = nRT, solving for whichever term is missing.
OpenpH Calculator
pH, pOH and both ion concentrations, on a log scale.
OpenHalf-Life Calculator
Exponential decay, and why it never reaches zero.
OpenPercent Yield Calculator
Actual over theoretical, and what a figure above 100 means.
OpenBoiling Point Calculator
Water's boiling point at altitude, from the pressure.
OpenAbout science & engineering calculations
Physics and chemistry calculations are exact in a way most of this site is not. There is no supplier variation, no regional rate, no fee schedule that changed last quarter — a z-score of 2 is a z-score of 2, and one mole of any gas at standard conditions occupies 22.41 litres whether it is helium or carbon dioxide.
What these tools carry instead is an idealisation. Free fall ignores air resistance, projectile motion ignores drag, the ideal gas law ignores molecular volume, and a voltage divider assumes nothing is drawing current from it. Each of those is exactly right about a world slightly simpler than the real one, and knowing which simplification a page has made is the difference between using its answer and being misled by it. Every page here states its own.
Constants are handled the same way. Standard gravity is 9.80665 m/s² by definition rather than by measurement, and real local gravity runs from about 9.78 at the equator to 9.83 at the poles — so it appears as an editable field rather than a hard-coded fact.
Which one do you need?
I need to work out motion or energy
Speed, distance and time determine each other completely, so any two give the third. For anything accelerating, the velocity and acceleration calculators use the SUVAT relations and report the result in g as well as m/s² — 0.57 g is legible in a way 5.6 m/s² is not. Kinetic energy is where the square matters: doubling speed quadruples the energy, which is why braking distance rises so much faster than speed.
I am building a circuit
The LED resistor calculator rounds up to the next standard value rather than the nearest, because rounding down pushes current past the LED's rating. The resistor and capacitor pages cover series and parallel, which use opposite formulas — resistors add in series, capacitors add in parallel. For filters and timing, the RC time constant page explains where the 63.2% figure comes from.
I am making up a solution
Molarity is moles per litre of solution, not of solvent, so a 1 M solution is topped up to the mark rather than made by adding solute to a full litre. The dilution calculator gives the diluent to add rather than the final volume, which is the number you actually need at the bench.
I need pressure, density or buoyancy
Hydrostatic pressure depends only on depth, fluid density and gravity — the shape and width of the container are irrelevant, which is why a narrow pipe and a wide lake press equally hard at the same depth. The density calculator reports buoyancy as three states rather than two, because a material at exactly the density of water is neutrally buoyant rather than sinking.