Physics Unit Converter
Convert between physics units across five categories: energy (Joules, kWh, eV), force (Newtons, lbf), power (Watts, horsepower), pressure (Pascal, bar, PSI), and velocity (m/s, km/h, mph). No signup, runs entirely in your browser.
How to Use the Physics Unit Converter
- 1Pick a category: energy, force, power, pressure, or velocity.
- 2Select the from and to units — e.g. kilowatt-hours to Joules, or PSI to bar.
- 3Enter the value; the conversion updates instantly. E-notation is fine for very large or small quantities.
Worked Example: Making Sense of an EV Spec Sheet
An electric car brochure lists a 60 kWh battery, a 150 kW motor, and recommends 36 psi tire pressure — three different unit systems on one page. Converting the battery: 60 kWh × 3.6 MJ/kWh = 2.16 × 10⁸ J of stored energy. The motor: 150 kW ÷ 0.7457 ≈ 201 hp, which is the number a petrol-car buyer can compare against. The tires: 36 psi × 6.895 ≈ 248 kPa, or about 2.5 bar — the unit European pressure gauges display.
A useful sanity check ties energy and power together: at highway cruise the car might draw 20 kW, so the 60 kWh pack lasts 60 / 20 = 3 hours. Units are the grammar of physics — most calculation errors are unit errors, and converting everything to SI base units (Joules, Watts, Pascals, m/s) before working a problem is the single most effective way to avoid them.
Physics Unit Tips
Energy in everyday life
A typical home uses ~900 kWh/month. One kWh = 3,600,000 J. A cup of food contains ~200 kcal = ~837,000 J of chemical energy — but our bodies convert it at ~20–25% efficiency.
Pressure at altitude
Atmospheric pressure is 1 atm = 101,325 Pa at sea level. It drops ~1.2% per 100 m gain. At cruising altitude (10,000 m), cabin pressure is ~75 kPa or about 0.75 atm.
Force in engineering
Structural engineers often work in kN or MN. A typical car weighs ~15 kN (about 1500 kg × 9.81). Bridge loads are calculated in MN and kN/m distributed loads.
Speed of sound in m/s
343 m/s = 1235 km/h = 767 mph. Supersonic aircraft exceed Mach 1 (343 m/s). The Concorde cruised at Mach 2 ≈ 686 m/s ≈ 2470 km/h.
Frequently Asked Questions
What units of energy does this converter support?
Joules (J), kilojoules (kJ), calories (cal), kilocalories (kcal), watt-hours (Wh), kilowatt-hours (kWh), electronvolts (eV), BTU, and ergs. The SI base unit is the Joule.
What is the difference between a calorie and a kilocalorie?
One kilocalorie (kcal) = 1000 calories (cal). Food calories are actually kilocalories — a "200-calorie" snack contains 200 kcal or 200,000 cal. One kcal = 4184 J.
How many Watts is one horsepower?
One mechanical horsepower = 745.7 Watts. So a 100 hp engine produces about 74.57 kW. Electric motors are often rated in kW while combustion engines use hp — this converter bridges the two.
What pressure units are supported?
Pascals (Pa), kilopascals (kPa), megapascals (MPa), bar, atmospheres (atm), PSI (pounds per square inch), and millimeters of mercury (mmHg/Torr). 1 atm = 101,325 Pa = 14.696 PSI.
How do I convert km/h to m/s?
Divide by 3.6: 100 km/h = 100/3.6 ≈ 27.78 m/s. The converter does this automatically. 1 m/s = 3.6 km/h.
Is my data stored?
No. All calculations run locally in your browser. No data is sent to any server.