Physics CalculatorsFree Physics Formula Solvers
Physics calculators solve the equations of motion, force, energy, electricity, waves and heat for you — enter the values you know and get the unknown, in the right SI unit, with the formula and every step shown. Below are 41 free tools grouped into 8 branches of physics, from velocity and kinetic energy to Ohm’s law and time dilation.
Formulas cross-checked against OpenStax University Physics · constants from NIST CODATA 2022 · units per the BIPM SI Brochure
Built & maintained by Manzoor AhmadPharmacist & calculator developer · Updated
What is a physics calculator?
A physics calculator is an online tool that rearranges and solves a physics formula — such as F = ma, KE = ½mv² or V = IR — for whichever value is missing. It converts your units to SI, applies the equation with standard constants (g = 9.80665 m/s², c = 299,792,458 m/s), and returns the answer with its unit and the working steps, so you can check homework, lab results or real-world estimates in seconds.
Showing all 41 physics calculators
Motion & Kinematics Calculators
6 toolsKinematics describes how things move without asking why. These tools handle straight-line velocity and speed, SUVAT displacement, rotation in rad/s and rpm, and the top speed an object reaches when air drag catches up with gravity.
Velocity Calculator
Find velocity from displacement and time, or from initial velocity, acceleration and time.
v = Δd / Δt
Speed Calculator
Solve the speed–distance–time triangle for any missing value, with km/h, mph and m/s.
s = d / t
Displacement Calculator
Find how far an object moves from its start point under constant acceleration.
s = ut + ½at²
Angular Velocity Calculator
Convert rpm to rad/s and find angular velocity from angle, period or linear speed.
ω = Δθ / Δt
Terminal Velocity Calculator
Top falling speed of a skydiver, ball or raindrop, where drag balances weight.
vt = √(2mg / ρACd)
Pendulum Calculator
Period, frequency and length of a simple pendulum, on Earth or any other planet.
T = 2π√(L/g)
Force, Torque & Machine Calculators
9 toolsDynamics adds the why. These calculators cover friction on a surface, objects on a ramp, springs, air drag, turning forces, rotational inertia and the gears that trade speed for torque.
Friction Calculator
Static and kinetic friction force from the coefficient of friction and normal force.
f = μN
Inclined Plane Calculator
Forces, acceleration and friction for an object on a slope or ramp.
a = g(sinθ − μcosθ)
Hooke’s Law Calculator
Spring force, spring constant and extension, plus stored elastic energy.
F = kx
Drag Force Calculator
Aerodynamic drag on a car, cyclist or ball from speed, area and drag coefficient.
Fd = ½ρv²CdA
Impulse Calculator
Find impulse from force and contact time, or from a change in momentum.
J = FΔt = Δp
Torque Calculator
Turning force from lever-arm length, applied force and angle, in N·m or lb·ft.
τ = rF sinθ
Moment of Inertia Calculator
Rotational inertia of rods, discs, rings, spheres and boxes about any common axis.
I = Σmr²
Gear Ratio Calculator
Gear ratio, output speed and output torque for a gear pair or train.
GR = Nout / Nin
Gravitational Force Calculator
Newton’s law of universal gravitation between any two masses.
F = Gm₁m₂ / r²
Work, Power & Engine Calculators
3 toolsWork is energy moved by a force, and power is how fast that happens. Convert between joules, watts and horsepower, and turn engine torque and RPM into the numbers on a spec sheet.
Work Calculator
Work done by a force acting over a distance at any angle.
W = Fd cosθ
Power Calculator
Mechanical power from work and time, or from force and velocity.
P = W / t
Horsepower Calculator
Convert torque and RPM to horsepower, or watts to mechanical and metric hp.
hp = T × rpm / 5252
Fluids & Pressure Calculators
3 toolsTyres, hydraulic presses, boats and pipes all obey a short list of fluid rules. Work out pressure at depth, Archimedes’ buoyant force and how much fluid a pipe moves per second.
Pressure Calculator
Pressure from force and area, plus hydrostatic pressure at a given depth.
P = F / A
Buoyancy Calculator
Archimedes’ buoyant force and whether an object floats or sinks.
Fb = ρgV
Flow Rate Calculator
Volumetric flow rate from pipe diameter and velocity, in L/min, GPM or m³/s.
Q = A × v
Electricity & Electronics Calculators
8 toolsFrom sizing a cable run to picking a resistor for an LED, these tools cover the working maths of circuits: power, voltage drop, resistor networks, colour codes, capacitors and electric charge.
Watt Calculator
Convert between watts, volts and amps for DC and AC circuits.
P = VI
Voltage Drop Calculator
Voltage lost along a cable run from wire size, length and current.
Vd = I × Rwire
Parallel Resistor Calculator
Equivalent resistance of resistors in parallel and in series.
1/R = 1/R₁ + 1/R₂ + …
Resistor Color Code Calculator
Decode 4-, 5- and 6-band resistor colours into ohms and tolerance.
R = (d₁d₂) × 10ⁿ
LED Resistor Calculator
The series resistor an LED needs for a given supply voltage and current.
R = (Vs − Vf) / I
RC Filter Calculator
Cutoff frequency, component values, and gain and phase of RC low-pass and high-pass filters.
fc = 1 / 2πRC
Capacitor Calculator
Capacitors in series and parallel, stored charge, energy and RC time constant.
Q = CV
Coulomb’s Law Calculator
Electrostatic force between two point charges at any distance.
F = kq₁q₂ / r²
Waves, Sound & Optics Calculators
6 toolsEvery wave is described by its frequency, wavelength and speed. Use these for acoustics, sirens that change pitch, the speed of sound at any temperature, refraction and lenses.
Frequency Calculator
Frequency from period, or from wavelength and wave speed.
f = 1 / T
Speed of Sound Calculator
Speed of sound in air at any temperature, and in water and common solids.
v ≈ 331.3√(1 + T/273.15)
Doppler Effect Calculator
Observed frequency when a sound source or listener is moving.
f′ = f(v + vo)/(v − vs)
Decibel Calculator
Add, compare and convert sound levels and power ratios in dB.
L = 10 log₁₀(P/P₀)
Snell’s Law Calculator
Refraction angle and refractive index when light crosses a boundary.
n₁sinθ₁ = n₂sinθ₂
Thin Lens Calculator
Image distance, focal length and magnification from the lens equation.
1/f = 1/do + 1/di
Heat & Thermodynamics Calculators
2 toolsHeat makes solids grow and drives phase changes. Find how far a rail or pipe expands, and how much energy it takes to melt ice or boil water.
Thermal Expansion Calculator
How much a solid grows in length or volume when it warms up.
ΔL = αL₀ΔT
Latent Heat Calculator
Energy to melt, freeze, boil or condense a substance with no temperature change.
Q = mL
Modern Physics & Astrophysics Calculators
4 toolsRelativity, photons and orbits. These tools take the famous equations of the 20th century and make them usable in a few clicks.
E=mc² Calculator
Mass–energy equivalence: convert any mass into its rest energy.
E = mc²
Time Dilation Calculator
Special-relativity time dilation and the Lorentz factor at any speed.
Δt′ = γΔt
Photon Energy Calculator
Energy of a photon from its wavelength or frequency, in joules and eV.
E = hf = hc/λ
Orbital Velocity Calculator
Speed and period of a circular orbit around Earth or any planet.
v = √(GM / r)
More physics calculators in our Science hub
Some of the most-used physics tools on DexoCalc were built first for our Science Calculators hub, next to the chemistry and biology tools they are often used with. Rather than build them twice, we link them here. Together with the 41 tools above, that gives you 56 physics calculators in one place.
Acceleration Calculator
Final Velocity Calculator
Free Fall Calculator
Projectile Motion Calculator
Force Calculator
Momentum Calculator
Centripetal Force Calculator
Kinetic Energy Calculator
Potential Energy Calculator
Density Calculator
Ohm’s Law Calculator
Wavelength Calculator
Specific Heat Calculator
Half-Life Calculator
Escape Velocity Calculator
Which physics calculator do I need?
Start with what you already know. Find your starting values in the left column and the quantity you are trying to find — the right column points you to the tool that solves it directly.
| You know | You want | Use this calculator |
|---|---|---|
| Distance and time | Speed or travel time | Speed Calculator |
| Mass and acceleration | Net force in newtons | Force Calculator |
| Launch speed and angle | Range, height, flight time | Projectile Motion Calculator |
| Mass and speed | Energy of motion (J) | Kinetic Energy Calculator |
| Engine torque and RPM | Horsepower | Horsepower Calculator |
| Voltage and resistance | Current and power | Ohm’s Law Calculator |
| Wire length, size, current | Voltage lost on the run | Voltage Drop Calculator |
| Starting amount, half-life | Amount left after time t | Half-Life Calculator |
Worked example: one braking car, five physics calculators
Physics problems rarely stop at one formula. Here is how a single real-world question chains through several tools on this page — every number below is reproducible in the linked calculators.
The question
A 1,200 kg car travelling at 25 m/s (90 km/h) brakes to a stop over 50 m. How much momentum and energy does it carry, what braking force is needed, and how much power do the brakes absorb?
Takeaway: at double the speed (50 m/s) the same car carries four times the kinetic energy — 1.5 MJ — because KE grows with v². The same insight explains why the work the brakes must do rises so sharply with speed.
Physics formulas cheat sheet
The ten equations behind the most-used calculators in this hub, with the variables and SI units each one expects.
| Quantity | Formula | Variables | SI unit |
|---|---|---|---|
| Velocity | v = Δd / Δt | displacement, time | m/s |
| Acceleration | a = (v − u) / t | final & initial velocity, time | m/s² |
| Force | F = ma | mass, acceleration | N (kg·m/s²) |
| Momentum | p = mv | mass, velocity | kg·m/s |
| Kinetic energy | KE = ½mv² | mass, speed | J |
| Potential energy | PE = mgh | mass, gravity, height | J |
| Work | W = Fd cosθ | force, distance, angle | J |
| Power | P = W / t | work, time | W (J/s) |
| Ohm’s law | V = IR | current, resistance | V |
| Wave speed | v = fλ | frequency, wavelength | m/s |
Physical constants used in every calculator
All tools share one constants file so results stay consistent across the hub. Values follow the 2022 CODATA recommended values published by NIST; since the 2019 SI redefinition, several are now exact by definition.
| Constant | Symbol | Value | Status |
|---|---|---|---|
| Speed of light in vacuum | c | 299,792,458 m/s | Exact |
| Standard gravity | gn | 9.80665 m/s² | Defined (editable in tools) |
| Newtonian gravitational constant | G | 6.67430 × 10⁻¹¹ m³·kg⁻¹·s⁻² | Measured |
| Planck constant | h | 6.62607015 × 10⁻³⁴ J·s | Exact |
| Elementary charge | e | 1.602176634 × 10⁻¹⁹ C | Exact |
| Boltzmann constant | kB | 1.380649 × 10⁻²³ J/K | Exact |
| Coulomb constant | ke | 8.9875517862 × 10⁹ N·m²/C² | Derived from ε₀ |
| Speed of sound (dry air, 20 °C) | vs | ≈ 343 m/s | Typical value |
How we build and test every physics calculator
Search engines and readers both deserve to know how a tool reaches its answer. This is the release standard every calculator in this hub has to meet before it goes live.
- Source the formulaEach equation is taken from an open, peer-reviewed textbook (OpenStax University Physics and College Physics) and cross-checked against HyperPhysics and NASA Glenn’s educational references.
- Compute in SI, convert at the edgesInputs in mph, feet, pounds, psi or lb·ft are converted to SI before the maths and back again afterwards, which removes the most common source of homework errors.
- Test against published examplesA calculator must reproduce worked examples from the textbooks it cites before release, and is re-run whenever its code changes.
- Handle edge cases honestlyZero, negative and physically impossible inputs (an angle over 90° for range, a speed above c) return a clear message instead of a misleading number.
- Show the workingEvery result shows the formula, the substituted values and the steps, rounded for reading but with full precision available.
- Review and date itPages carry a visible “updated” date, and reader-reported issues are fixed and logged on the next update.
Manzoor Ahmad
Pharmacist turned Web Developer & Calculator Engineer · 13+ years in web developmentI’m a pharmacist by training who turned into a full-time tech geek, and I design, code and maintain every calculator on DexoCalc. My pharmacy degree covered physical pharmacy — fluids, heat, pressure, light and kinetics — so I know these equations from the lab as well as from the keyboard. Where that background is directly relevant, as with IV flow rates, latent heat in freeze-drying and UV-visible photon energies, I say so on the page.
I’m not a physicist, and I won’t pretend to be. That is exactly why every formula here is traced to an open university textbook or NIST reference data, listed below, and tested against published worked examples before it goes live. If you spot an error, tell me — corrections are fixed and dated on the next update.
Physics calculators: frequently asked questions
A physics calculator is a tool that solves a specific physics equation for you. You enter the values you know — such as mass, speed or voltage — and it returns the unknown quantity with the correct SI unit, the formula used and the working steps.
Yes. Every calculator in the dexocalc.com physics hub is free, needs no sign-up and runs directly in your browser, so the numbers you enter are not sent to a server.
Each calculator works in SI units internally (metres, kilograms, seconds, newtons, joules, volts and so on) and converts common alternatives such as mph, feet, pounds, psi and lb·ft before and after the calculation.
The maths runs in double-precision floating point, and physical constants come from the 2022 CODATA values published by NIST. Results are shown rounded for readability, with the full-precision value available. Real-world answers are limited by the accuracy of your inputs and by the assumptions of each formula, such as ignoring air resistance.
By default we use standard gravity, g = 9.80665 m/s². Where it matters, you can change it to a local value or to the gravity of another planet or moon.
Yes — they are designed for it. Use them to check your own working rather than to replace it: each tool shows the formula and steps so you can see exactly where your answer differs.
Speed is how fast something moves and has size only. Velocity is speed in a specific direction, so it is a vector. A car driving one full lap of a track has an average speed above zero but an average velocity of zero, because it ends where it started.
Mass is the amount of matter in an object, measured in kilograms, and it is the same everywhere. Weight is the gravitational force on that mass, W = mg, measured in newtons, so it changes from Earth to the Moon.
Use Newton’s second law, F = ma. Multiply mass in kilograms by acceleration in m/s² to get force in newtons. A 1,200 kg car accelerating at 2 m/s² needs a net force of 2,400 N.
Kinetic energy is KE = ½mv². Because speed is squared, doubling speed quadruples kinetic energy — which is why stopping distances grow so quickly at higher speeds.
Ohm’s law states that voltage equals current multiplied by resistance, V = IR. Knowing any two of the three lets you find the third; adding P = VI also gives electrical power.
Every calculator is designed, coded and maintained by Manzoor Ahmad, a pharmacist turned web developer with more than 13 years of experience building web tools. Formulas are taken from open university textbooks and NIST reference data, and each tool is tested against published worked examples before it goes live.
References & sources
- Ling, S. J., Sanny, J. & Moebs, W. University Physics, Volumes 1–3. OpenStax, Rice University.
- Urone, P. P. & Hinrichs, R. College Physics 2e. OpenStax, Rice University.
- Tiesinga, E., Mohr, P. J., Newell, D. B. & Taylor, B. N. The 2022 CODATA Recommended Values of the Fundamental Physical Constants. NIST.
- Bureau International des Poids et Mesures. The International System of Units (SI Brochure), 9th edition.
- NASA Glenn Research Center. Beginner’s Guide to Aeronautics (motion, forces and fluids).
- Nave, R. HyperPhysics. Georgia State University.
Disclaimer: These calculators are educational tools. They use idealised models (for example, no air resistance unless stated) and are not a substitute for professional engineering, electrical or safety calculations. For wiring, structural or pressure-vessel work, always follow your local codes and consult a qualified professional.