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Physics Formula Sheet (with Unit Conversions)

The core physics formulas used in high school and intro college physics, each with its SI units and US customary conversion — so you can check unit conversions while solving problems.

Speed

e.g. mph, km/h, m/s

v = d / t

Example: 120 miles in 2 h → v = 60 mph = 96.6 km/h

Density

e.g. g/cm³, kg/m³

ρ = m / V

Example: Water ≈ 1 g/cm³ = 1,000 kg/m³ (standard reference value)

Force (Newton’s 2nd law)

newton (N)

F = m × a

Example: 10 kg at 2 m/s² → F = 20 N

Power

watt (W)

P = W / t

Example: 900 J in 3 s → P = 300 W ≈ 0.402 hp

Electrical power

watt (W)

P = V × I

Example: 120 V × 5 A = 600 W

Horsepower ↔ watts

1 hp = 745.6999 W

Example: 1 hp = 745.6999 W; 1 kW ≈ 1.341 hp (exact NIST-derived constants)

Kinetic energy

joule (J)

KE = ½ × m × v²

Example: 2 kg at 3 m/s → KE = ½ × 2 × 9 = 9 J

Practice the conversion too

These examples convert US customary to metric using the exact NIST / SI constants. Open a converter to check any value:

Browse all converters →

Frequently Asked Questions

What units do I get if I multiply kg × m/s²?

kg × m/s² = newton (N), the SI unit of force. 1 N = 1 kg·m/s². In US customary, 1 pound-force ≈ 4.448 N.

How do I convert horsepower to watts?

1 hp = 745.6999 W (exact). To convert kW to hp, divide by 0.7456999 (1 kW ≈ 1.341 hp).

Why is density written both as g/cm³ and kg/m³?

They are the same substance in different units: 1 g/cm³ = 1,000 kg/m³. Water is 1 g/cm³ = 1,000 kg/m³.

More formula sheets

📐 Geometry 🌡️ Temperature 🔢 Metric Prefixes 🔁 Conversion Formulas

Last Updated 2026 | Formulas are standard textbook content; conversion constants trace to NIST SP 330 & the BIPM SI Brochure.