Physics Solver
Pick a formula, say which quantity you want to find, enter the others with their units and see the answer with the working.
Equation:
Typing questions in words and solving from a photo are planned. Today this tool solves questions written as formulas.
What This Tool Can and Cannot Do
This tool works with the 35 formulas listed below. You choose a formula, choose the quantity to find, and enter the other values, each with its own unit. It converts everything to SI units, solves the formula, and shows the answer with the working. It does not read word problems, drawings or photos, and it does not choose a formula for you. Check that the formula fits your situation, and check units and sign conventions. Rounding is only applied to what is shown; the calculation itself keeps full precision.
Formulas Included
- Motion: Velocity, acceleration and time (v = u + a·t); Displacement from initial speed and acceleration (s = u·t + ½·a·t²); Velocity without time (v² = u² + 2·a·s); Displacement from average velocity (s = (u + v)·t / 2); Average speed (v = d / t)
- Projectile motion (level ground, no air resistance): Time of flight (T = 2·v₀·sin θ / g); Maximum height (H = v₀²·sin²θ / (2g)); Range (R = v₀²·sin 2θ / g)
- Forces and energy: Newton's second law (F = m·a); Weight (W = m·g); Momentum (p = m·v); Work done by a force (W = F·d·cos θ); Power (P = W / t); Kinetic energy (K = ½·m·v²); Gravitational potential energy (U = m·g·h); Impulse (J = F·t); Newton's law of gravitation (F = G·m₁·m₂ / r²)
- Circular motion: Centripetal acceleration (a = v² / r); Centripetal force (F = m·v² / r)
- Pressure and density: Density (ρ = m / V); Pressure (P = F / A); Pressure at a depth in a fluid (P = ρ·g·h)
- Electricity: Ohm's law (V = I·R); Electric power (P = V·I); Resistors in series (2 or 3) (R_total = R₁ + R₂ + R₃); Resistors in parallel (2 or 3) (1/R_total = 1/R₁ + 1/R₂ + 1/R₃); Coulomb's law (magnitudes) (F = k·q₁·q₂ / r²); Charge and current (Q = I·t)
- Waves and optics: Wave speed (v = f·λ); Lens and mirror equation (real-is-positive) (1/f = 1/u + 1/v); Snell's law of refraction (n₁·sin θ₁ = n₂·sin θ₂)
- Heat and gases: Heat needed to change temperature (Q = m·c·ΔT); Ideal gas law (P·V = n·R·T); Boyle's law (constant temperature) (P₁·V₁ = P₂·V₂); Charles's law (constant pressure) (V₁ / T₁ = V₂ / T₂)
Constants Used
Gravity g = 9.80665 m/s² (standard gravity; you can switch to 9.81 m/s²). Gravitational constant G = 6.6743 × 10⁻¹¹ N·m²/kg². Coulomb constant k = 8.9875517923 × 10⁹ N·m²/C². Gas constant R = 8.314462618 J/(mol·K). G and k are the CODATA 2018 recommended values; g is the standard value by definition and R follows from the 2019 SI definitions.
How to Use the Physics Solver
Use it for homework checks, quick estimates or revision. It does the unit conversion and the algebra, so you can focus on whether the formula fits your problem.
- Pick a formula: Choose it from the list. The equation is shown below the menu.
- Choose what to solve for: Select the quantity you want to find. That row turns into the answer row and its unit menu sets the unit of the result.
- Enter the other values: Type a number for every other quantity and pick its unit. Use a dot for decimals; you can write 1.5e3 for 1500.
- Calculate: Press Calculate or Enter. Read the answer and the working, and copy it if you need it.
Key Features
- Formulas as data: 35 formulas, each solvable for every one of its quantities.
- Unit conversion: Lengths, speeds, forces, energies, pressures, temperatures (°C, K, °F), angles and more.
- Working shown: The formula in symbols, then with your numbers put in, in SI units.
- Clear refusals: Impossible inputs give a plain message, never NaN or a blank.
- Private by design: Calculated in your browser. Nothing is sent or stored.
Frequently Asked Questions
Which formulas are included?
There are 35 formulas in eight groups: motion, projectile motion, forces and energy, circular motion, pressure and density, electricity, waves and optics, and heat and gases. The full list is shown on this page. Anything that is not on the list cannot be solved here.
Why does every value have a unit, and what do the significant figures do?
Each value has its own unit menu, so you can mix, for example, km/h and seconds. The tool converts everything to SI units before it calculates and gives the answer in the unit you pick. The significant figures setting (3, 4 or 6) only changes how the answer is rounded on screen.
Which value of g is used?
The standard value 9.80665 m/s². Formulas that use gravity show a menu where you can switch to the rounded value 9.81 m/s². Gravity differs a little from place to place, so use your own value if your problem gives one.
What does projectile motion assume?
The launch and landing points are at the same height, the ground is flat, there is no air resistance, and gravity is constant. The three projectile formulas (time of flight, maximum height and range) are only valid under these assumptions.
Why do I sometimes get two answers?
Some formulas are quadratic. For example, solving s = ut + ½at² for time can give two values, and a range can be reached with a low or a high launch angle. Both are shown, and answers that are physically impossible, such as a negative time, are marked as not valid.
Why do I get a message instead of a number?
The tool refuses cases that have no physical answer: a temperature at or below absolute zero, a negative mass, a division by zero, light that is totally internally reflected, or a launch speed that cannot reach the range you typed. In the lens and mirror formula distances use the real-is-positive convention: real objects and real images are positive, and the focal length is positive for a converging lens or a concave mirror and negative for a diverging lens or a convex mirror.