All calculatorsWatt Calculator
Calculate power (watts) using energy over time, force × velocity, or torque × angular speed. Includes optional step-by-step plus a mini power scale.
Background
A watt (W) measures how fast energy is transferred or used: 1 W = 1 J/s. Different situations use different (but equivalent) formulas — this calculator lets you pick the one that matches your problem.
How to use this calculator
- Pick the method that matches your problem: E/t, F·v, or τ·ω.
- Enter values (units can differ; the calculator converts them).
- Click Calculate to see watts plus common conversions.
How this calculator works
- Convert inputs to consistent base units (J, s, N, m/s, N·m, rad/s).
- Apply the selected power formula to compute watts.
- Convert watts into common outputs: kW, MW, and hp.
- Show a mini power-scale visualization to help you “feel” the magnitude.
Formula & Equation Used
Energy over time: P = E / t
Force times velocity: P = F · v
Rotational power: P = τ · ω
Unit identity: 1 W = 1 J/s.
Example Problems & Step-by-Step Solutions
Example 1 — E/t
A device uses 1200 J of energy in 30 s.
- Use P = E/t
- P = 1200 / 30 = 40 W
Example 2 — F·v
A force of 150 N pushes an object at 3.5 m/s.
- Use P = F·v
- P = 150 × 3.5 = 525 W
Example 3 — τ·ω
A motor produces 12 N·m of torque at 1800 rpm.
- Convert rpm to rad/s: ω = 1800·2π/60 ≈ 188.50 rad/s
- Compute power: P = τ·ω = 12×188.50 ≈ 2262 W
Frequently Asked Questions
Q: What is a watt?
A watt is a rate of energy transfer: 1 W = 1 joule per second.
Q: Why are there multiple formulas for power?
They describe the same idea in different contexts: energy changes (E/t), linear motion (F·v), and rotation (τ·ω).
Q: Can power be negative?
Yes. Negative power can mean energy is being removed from a system (like braking) depending on your sign convention.
Q: Is horsepower the same as watts?
They measure the same thing (power). This calculator converts watts to horsepower for convenience.
