Terminal Velocity Calculator
The speed at which drag balances weight and a falling object stops accelerating — for a skydiver, a raindrop or anything else.
Falling objects do not accelerate for ever.
How the terminal velocity calculator works
Falling objects do not accelerate for ever. Drag grows with the square of speed, so it climbs until it equals weight, and from then on the object falls at a constant terminal velocity: √(2mg ÷ ρ A C_d).
The consequences are dramatic and familiar. A skydiver falling flat reaches about 55 m/s; the same person head-down, with a fraction of the area, exceeds 90. A raindrop reaches perhaps 9 m/s, which is why rain does not injure anyone despite falling a kilometre or more.
Formula: v = √(2mg ÷ (ρ × A × C_d))
Worked examples
| Inputs | Terminal velocity | Note |
|---|---|---|
| A skydiver falling flat | 42.776 m/s | 42.7 m/s — about 154 km/h |
| The same skydiver head-down | 100.825 m/s | over 100 m/s |
| A raindrop | 14.327 m/s | about 9 m/s |
FAQFrequently asked questions
What is terminal velocity?
The speed at which air resistance exactly balances weight, so the object stops accelerating and falls at a constant rate.
How fast does a skydiver fall?
About 55 m/s (200 km/h) belly-down, and over 90 m/s head-down, because the frontal area is much smaller.
Why does rain not hurt?
A raindrop reaches terminal velocity at about 9 m/s within a few metres, however far it falls.
Does a heavier object fall faster?
In air, yes — terminal velocity goes with the square root of mass for the same shape. In a vacuum, no.
How long does it take to reach?
A skydiver is within 95% of terminal velocity after about 12 seconds and 450 metres.
Where these figures come from
- NIST — CODATA 2018 fundamental physical constants — G, g₀, R, c
- NIST Special Publication 811 — Guide for the use of the International System of Units — unit conversions
- The Engineering ToolBox — material properties — specific heats, expansion coefficients, densities
- National Measurement Institute — Australia's measurement authority
Last checked: September 2026. Constants are the CODATA 2018 values; formulas are the standard textbook forms.