Answer first
What this calculator tells you
Calculate the fall time and impact speed of an object dropped from a height. Estimate how long a drop takes and how fast the object hits, ignoring air. Formula: Fall time = √(2h ÷ g); impact speed = √(2 × g × h), ignoring air resistance. At the worked-example inputs, the fall time (s) is 3.2. Holding every other input steady, moving drop height (m) from 40 to 60 moves the result from 2.9 to 3.5.
Transparent method
The formula
Estimate how long a drop takes and how fast the object hits, ignoring air.
Worked example
Example inputs
How to interpret the result
Without air resistance, an object dropped from rest falls a distance that grows with the square of the time. From 50 meters it lands after about 3.2 seconds at about 31 meters per second, roughly 113 kilometers an hour. Doubling the height does not double the time; it multiplies it by about 1.4. Real objects fall slower than this, and a light one with a large area falls much slower.
At the worked-example inputs the fall time (s) is 3.2. It rises with drop height (m) and falls as gravity (m/s²) increases.
These are textbook formulas for ideal conditions: no air resistance, no friction, gravity of 9.81 meters per second squared and gases that behave ideally. Real results differ, so treat them as first estimates and use the units the formulas expect (meters, kilograms, seconds).
Before you rely on it
What to check
Use the drop only where air is a minor effect. A feather or a parachute falls in a very different way from a stone.
The common error
Where people go wrong with free fall calculator
Assuming a heavier object lands first. Without air resistance, mass does not change the fall time, and a hammer and a feather land together.
Sensitivity evidence
How drop height (m) changes the fall time (s)
Holding every other input at the worked-example value, moving drop height (m) from 40 to 60 moves the fall time (s) from 2.9 to 3.5: a spread of 0.642, or 20% of the worked-example result.
| Drop height (m) | Fall time (s) | Impact speed (m/s) | Impact speed (km/h) |
|---|---|---|---|
| 40 | 2.9 | 28 | 100.9 |
| 45 | 3 | 29.7 | 107 |
| 50worked example | 3.2 | 31.3 | 112.8 |
| 55 | 3.3 | 32.8 | 118.3 |
| 60 | 3.5 | 34.3 | 123.5 |
Every input, tested
Which input moves the fall time (s) most
Of the 2 inputs, gravity (m/s²) moves the fall time (s) most (0.318 across the range tested) and drop height (m) moves it least (0.32).
| Input | Tested from | To | Fall time (s) at each end | Swing |
|---|---|---|---|---|
| Gravity (m/s²) | 9 | 11 | 3.3 to 3 | 0.318 (10.0%) |
| Drop height (m) | 45 | 55 | 3 to 3.3 | 0.32 (10%) |
Two variables at once
Fall time (s) by drop height (m) and gravity (m/s²)
Across the grid the fall time (s) runs from 2.6 to 3.9. Moving drop height (m) from 40 to 60 shifts it by 0.636 at the middle column, and moving gravity (m/s²) from 8 to 12 shifts it by 0.649 at the middle row, so gravity (m/s²) is the bigger lever here.
| Drop height (m) \ Gravity (m/s²) | 8 | 10 | 12 |
|---|---|---|---|
| 40 | 3.2 | 2.8 | 2.6 |
| 45 | 3.4 | 3 | 2.7 |
| 50 | 3.5 | 3.2 | 2.9 |
| 55 | 3.7 | 3.3 | 3 |
| 60 | 3.9 | 3.5 | 3.2 |
The highlighted cell is the worked example.
Step by step
The worked example, input by input
| Input | Value used | What it means |
|---|---|---|
| Drop height (m) | 50 | Enter the drop height (m) used in this calculation. |
| Gravity (m/s²) | 9.8 | Enter the gravity (m/s²) used in this calculation. |
| Fall time (s) | 3.2 | |
| Impact speed (m/s) | 31.3 | |
| Impact speed (km/h) | 112.8 | |
Inputs, definitions and assumptions
Drop height (m)
Enter the drop height (m) used in this calculation. The prefilled worked-example value is 50.
Gravity (m/s²)
Enter the gravity (m/s²) used in this calculation. The prefilled worked-example value is 9.8.
How to use this calculator
- 1Verify the inputs. Gather drop height (m) and gravity (m/s²) from your own documents; the prefilled values are examples.
- 2Save a baseline. The worked example puts the fall time (s) at 3.2. Store your own version of it as Scenario A.
- 3Test one change. Start with gravity (m/s²), the input with the biggest effect here: moving gravity (m/s²) from 9 to 11 takes the fall time (s) from 3.3 to 3, a swing of 10.0% of the worked-example figure.
- 4Check the extremes. At half the example gravity (m/s²) (4.9) the fall time (s) is 4.5; at double (19.6) it is 2.3.
People also ask
Frequently asked questions
How do you calculate free fall?
Fall time = √(2h ÷ g); impact speed = √(2 × g × h), ignoring air resistance. At the worked-example inputs the fall time (s) is 3.2.
What does the free fall result mean?
Estimate how long a drop takes and how fast the object hits, ignoring air. At the worked-example inputs the fall time (s) is 3.2. It rises with drop height (m) and falls as gravity (m/s²) increases.
How much does drop height (m) change the fall time (s)?
Holding every other input at the worked-example value, moving drop height (m) from 40 to 60 moves the fall time (s) from 2.9 to 3.5, a spread of 0.642.
What are the limits of this free fall calculator?
These are textbook formulas for ideal conditions: no air resistance, no friction, gravity of 9.81 meters per second squared and gases that behave ideally. Real results differ, so treat them as first estimates and use the units the formulas expect (meters, kilograms, seconds). The tables on this page test drop height (m) only from 40 to 60; a value outside that range is not tabulated here.
Which input moves the fall time (s) most in the free fall calculator?
Ranked by how far each moves the fall time (s) across the range tested: gravity (m/s²) (0.318, 10.0%) and drop height (m) (0.32, 10%).
If I double gravity (m/s²) in the free fall calculator, does the fall time (s) double?
Doubling it from 9.8 to 19.6 takes the fall time (s) from 3.2 to 2.3, which is 0.71 times the worked-example figure. So it falls instead of rising. Halving it to 4.9 gives 4.5.
How much does gravity (m/s²) matter in the free fall calculator?
The worked example uses 9.8. With the other inputs left at the worked example, moving gravity (m/s²) from 9 to 11 takes the fall time (s) from 3.3 to 3, a swing of 10.0% of the worked-example figure.
Which inputs change the impact speed (m/s) in the free fall calculator?
At the worked-example inputs it is 31.3. Drop height (m) takes it from 29.7 to 32.8 and gravity (m/s²) takes it from 30 to 33.2.
Which inputs change the impact speed (km/h) in the free fall calculator?
At the worked-example inputs it is 112.8. Drop height (m) takes it from 107 to 118.3 and gravity (m/s²) takes it from 108 to 119.4.
Do these physics calculators include air resistance?
No. They use the textbook formulas, which assume no air resistance and no friction. A real object falls or flies less far than the result, and a light object with a large surface is affected most.
Sources and evidence
Free Calculators Online is independent and is not affiliated with or endorsed by the source organizations. Educational estimates only.