Free Physics & Engineering Calculators

Mechanics, electricity, waves, optics, thermodynamics and fluids — every page deriving the result from the formula and printing the working, not just the answer.

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# 1 tool

555 Timer Calculator Computes 555 timer frequency, period, duty cycle and pulse width, and solves for parts.

A 2 tools

Acceleration Calculator Calculates acceleration from velocity change, from distance and time, or from force and mass. Angular Velocity Calculator Converts RPM, rad/s and tangential speed, and finds angular velocity from swept angle and time.

B 3 tools

Bernoulli Equation Calculator Solves Bernoulli's equation for pressure, velocity or elevation at a second point on a streamline. Breaker Size Calculator Sizes a circuit breaker from load amps, voltage and the continuous-load factor. Buoyancy Calculator Computes buoyant force, submerged fraction and apparent weight for an object in a fluid.

C 3 tools

Centripetal Force Calculator Computes centripetal force and acceleration from mass, radius and speed or angular velocity. Collision Momentum Calculator Solves 1-D elastic and inelastic two-body collisions using conservation of momentum. Coulomb's Law Calculator Computes the electrostatic force between two point charges, with a medium permittivity input.

D 4 tools

Density Calculator Finds density, mass or volume from the other two, with a built-in substance library. Dew Point Calculator Finds dew point from temperature and relative humidity using the Magnus approximation. Doppler Effect Calculator Find the observed frequency for a moving source, a moving observer or both, for sound and light. Drag Force Calculator Work out aerodynamic drag from speed, density, area and drag coefficient, plus the power it costs.

E 3 tools

Electric Field Calculator Compute electric field strength from a point charge, the force on a charge, or a parallel-plate field. Electrical Power Calculator Derive real, apparent and reactive power from voltage, current, resistance and power factor. Escape Velocity Calculator Get escape velocity, surface gravity and orbital speed from a body's mass and radius.

F 4 tools

Flow Rate Calculator Relate pipe area, fluid velocity, volumetric flow and mass flow, solving for whichever is missing. Force Calculator Solve Newton's second law for force, mass or acceleration, with weight and g-force alongside. Free Fall Calculator Get fall time, impact speed and impact energy from a drop height, in a vacuum or with drag. Friction Force Calculator Find friction force, normal force or the coefficient of friction from any two of them.

G 2 tools

Gear Ratio Calculator Compute overall gear ratio, output speed and output torque across a multi-stage gear train. Gravitational Force Calculator Find the gravitational pull between two masses, plus their accelerations and potential energy.

H 3 tools

Heat Index Calculator Get the NOAA heat index from temperature and humidity, with the NWS heat risk category. Hooke's Law Calculator Solve F = kx for force, spring constant or extension, with the stored elastic energy shown. Hydrostatic Pressure Calculator Calculate gauge and absolute fluid pressure at any depth from density, depth and gravity.

K 2 tools

Kepler's Third Law Calculator Relate orbital period, semi-major axis and central mass for any two-body orbit. Kinetic Energy Calculator Compute kinetic energy from mass and velocity, or solve for either of the other two.

L 3 tools

LC Resonant Frequency Calculator Find an LC circuit's resonant frequency, or the inductor or capacitor a target needs. LED Resistor Calculator Sizes the current-limiting resistor for an LED and gives the power rating it must survive. Lumen to Lux Calculator Converts lumens to lux and candela using beam angle and distance, and sizes room lighting.

M 2 tools

Mass Energy Equivalence Calculator Computes rest energy from mass with E = mc2, and the mass equivalent of a given energy. Momentum Calculator Solves p = mv for momentum, mass or velocity and shows impulse and kinetic energy.

O 1 tool

Ohm's Law Calculator Solves V = IR with P = VI from any two known values among volts, amps, ohms and watts.

P 6 tools

Photon Energy Calculator Computes photon energy in joules and electronvolts from wavelength or frequency. Pipe Flow Calculator Computes velocity, flow rate and friction pressure drop for a full pipe running liquid. Potential Energy Calculator Computes gravitational potential energy from mass, height and gravity, solving any way. Power Factor Calculator Relates real, reactive and apparent power and sizes the capacitor to correct power factor. Pressure Calculator Solve for pressure, force or area from the other two, with results in pascals, psi and bar. Projectile Motion Calculator Solve projectile range, flight time, peak height and impact speed with separate launch and landing heights.

R 4 tools

Relative Humidity Calculator Get relative humidity from a dew point, a wet-bulb reading or vapour pressures, using the Buck equation. Resistor Color Code Calculator Decode 3, 4, 5 and 6-band resistor colours to resistance and tolerance, or turn a value back into bands. Resistor Combination Calculator Find equivalent resistance for resistors in series, in parallel or in a mixed two-branch network. Reynolds Number Calculator Work out the Reynolds number and flow regime from density, viscosity, velocity and length.

S 8 tools

Schwarzschild Radius Calculator Find the Schwarzschild radius of any mass, with horizon density, Hawking temperature and lifetime. Simple Harmonic Motion Calculator Get period, frequency, displacement, velocity, acceleration and energy for a mass-spring oscillator. Simple Pendulum Calculator Get pendulum period, frequency and bob speed from length and gravity, with the small-angle error. Snell's Law Calculator Find the refraction angle and critical angle from two refractive indices, with total internal reflection. Specific Heat Calculator Solves Q = mcΔT for any single unknown, with a sourced substance library and unit switching. Stopping Distance Calculator Splits total stopping distance into reaction distance and braking distance for any speed. Stress and Strain Calculator Computes axial stress, strain and Young's modulus from force, area, length and elongation. SUVAT Calculator Give any three of s, u, v, a and t and get the remaining two plus the equation used.

T 3 tools

Thin Lens Equation Calculator Solves the thin lens equation and reports magnification, orientation and image type. Time Dilation Calculator Finds dilated time and the Lorentz factor for any velocity given as a fraction of c. Torque Calculator Calculates torque from force, lever arm and angle, or solves for any missing term.

V 3 tools

Velocity Calculator Works out average velocity from displacement and time, or final velocity under acceleration. Voltage Divider Calculator Finds divider output voltage, sizes a resistor pair, and shows the effect of a real load. Voltage Drop Calculator Estimates voltage drop and percent drop across a cable run from material, size and current.

W 3 tools

Wavelength Calculator Convert between wavelength, frequency and wave speed for light, sound and any other wave. Wire Size Calculator Find the smallest AWG or mm2 conductor that carries your load within ampacity and voltage drop limits. Work Calculator Compute mechanical work in joules from force, displacement and the angle between them.

Y 1 tool

Young's Modulus Calculator Find Young's modulus from stress and strain, or predict how far a bar stretches under load.

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Solvers, not converters

This site already had unit converters for force, energy, power, pressure and the rest. A converter rescales one quantity; these pages derive a physical result from a formula and show the substitution. Where a converter sits next to a calculator, both are linked and the boundary is stated in a sentence, so the two never compete for the same question.

The assumptions are on the page

Most wrong answers in physics come from applying a valid formula outside its range. So the Bernoulli page names all four of its assumptions before it names a number, the pendulum states the small-angle approximation and how much error it introduces, the projectile tools say whether they assume a vacuum, and the free-fall page ships a real quadratic-drag model rather than pretending air does not exist.

Where a code or a standard governs

Breaker sizing, wire gauge, voltage drop and stopping distance are not purely physics questions — they are governed by codes that differ by country. Those pages cite the standard they used, state the jurisdiction, publish no ampacity table of their own, and say plainly that a licensed professional signs off the real installation.

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All 1141 free tools are organised into 22 categories.