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DIY Cost Tools

DIY Cost Tools

Free Fall Calculator

Estimate time and final speed for an object released from rest through a stated vertical height under constant gravity.

Enter every field, including explicit zeros when permitted. Decimal and scientific notation are accepted; commas, fractions and blanks are rejected. Each input must be finite and no larger than 1 billion in absolute value. Observe the stated units and domain limits.

Fall time (s)2.019619977
Impact speed magnitude (m/s)19.80570625

How to use this calculator

  1. Enter every quantity in the unit printed beside its field.
  2. Select Calculate or press Enter.
  3. Read the labeled results and compare them with the assumptions below.

Formula and method

For release from rest: t = √(2h/g) and v = √(2gh).

The calculation runs locally in your browser. If any entry is invalid or a mathematical condition is undefined, the prior result is hidden so it cannot be mistaken for a new answer.

Worked example

Using Drop height (m) = 20, Gravitational acceleration (m/s²) = 9.80665, the formula returns Fall time (s) = 2.019619977, Impact speed magnitude (m/s) = 19.80570625. The displayed default result is generated from these same inputs.

Limitations and safety

Ignores air resistance, buoyancy, rotation and changes in gravity. Never use this idealized result to plan drops, stunts or fall protection. Results use floating-point arithmetic and are displayed to about 10 significant digits; measurement uncertainty usually supports fewer. Verify units before relying on a result.

Frequently asked questions

Does mass affect the result?

Not in this ideal model. Without air resistance, all masses share the same acceleration at the same location.

Why might a measured result differ?

The formula isolates the stated model. Real systems can add uncertainty, losses, changing properties, geometry or forces that are not among the inputs.

How should I handle units?

Convert every value to the unit shown beside its field before calculating. A numerically valid value in the wrong unit will still produce a wrong result.

Review notes and reference

Reviewed October 3, 2026. The default example and an independent edge or scaling case were checked against expected values. The live script was also checked for blank, text, comma-formatted, non-finite and out-of-range entries. Method reference. Constants use the values stated in the formula. This page’s explanation and example are original.

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