Acceleration Converter (m/s², g, ft/s², Gal)
Convert acceleration between m/s², standard gravity (g), ft/s², and Gal, the unit used in geophysics and seismology. Everything runs in your browser.
How the conversion works
Every unit on this page is defined by how many meters per second squared it represents. The input is converted to m/s², then from m/s² into the target unit:
result = value × (m/s² per source unit) ÷ (m/s² per target unit)
Acceleration measures how quickly speed changes. An acceleration of 1 m/s² means the speed increases by one meter per second, every second. After three seconds the object is moving at 3 m/s.
What "g" actually means
The "g" in this converter is standard gravity, defined as exactly 9.80665 m/s². It is the conventional value for gravitational acceleration at the Earth's surface, and it is a unit of acceleration, not the gram, which is a unit of mass.
Expressing acceleration in g is convenient because it maps onto something people feel directly. At 1 g you experience your normal body weight. At 2 g you feel twice as heavy, at 0 g you feel weightless. This is why aviation, motorsport, and aerospace all quote g-forces rather than m/s².
The actual gravitational acceleration varies slightly by location, from about 9.78 m/s² at the equator to 9.83 m/s² at the poles, because the Earth is not a perfect sphere and rotation counteracts gravity more strongly at the equator. The standard value of 9.80665 is a fixed convention rather than a measurement of any particular place.
Quick reference table
| From | m/s² | g | ft/s² | Gal |
|---|---|---|---|---|
| 1 m/s² | 1 | 0.101972 | 3.28084 | 100 |
| 1 g | 9.80665 | 1 | 32.1740 | 980.665 |
| 1 ft/s² | 0.3048 | 0.031081 | 1 | 30.48 |
| 1 Gal | 0.01 | 0.00101972 | 0.0328084 | 1 |
Familiar accelerations
| Situation | Approximate acceleration |
|---|---|
| Elevator starting | 0.1 to 0.2 g |
| Ordinary car accelerating | 0.3 g |
| Emergency braking | 0.8 to 1 g |
| Sports car launch | 1 g |
| Roller coaster peak | 4 to 6 g |
| Fighter jet turn | up to 9 g |
| Formula 1 cornering | 4 to 6 g |
Practical examples
Calculating 0 to 100 km/h acceleration
Convert the speed to m/s and divide by the time. 100 km/h is 27.78 m/s, so a car reaching it in 5 seconds averages 27.78 ÷ 5 = 5.56 m/s², which is 0.57 g. A supercar doing it in 3 seconds averages 9.26 m/s², or 0.94 g, close to the traction limit of ordinary tires on dry asphalt.
That limit is why acceleration figures cluster: without downforce or specialized tires, roughly 1 g is as much grip as is available, so no amount of engine power alone can go much beyond it.
Braking distance
Deceleration is negative acceleration and follows the same arithmetic. A car braking at 8 m/s² from 100 km/h (27.78 m/s) needs 27.78 ÷ 8 = 3.5 seconds and covers about 48 meters, before adding reaction time. Doubling the speed quadruples the braking distance, since distance scales with the square of speed.
Earthquakes and the Gal
Seismology uses the Gal, equal to 1 cm/s² or 0.01 m/s², named after Galileo. Ground acceleration during earthquakes is reported in Gal or in percent of g. A strong earthquake might produce peak ground acceleration of 400 Gal, which is about 0.41 g. Building codes specify design accelerations in these terms.
Human tolerance to g-force
Sustained acceleration above roughly 5 g in the head-to-foot direction causes blood to pool in the lower body, leading to vision loss and eventually unconsciousness. Pilots counter this with g-suits and specific breathing techniques. Brief impacts are survivable at much higher levels: properly restrained occupants have survived crash decelerations above 40 g.
Frequently asked questions
What does "3g" mean?
Three times standard gravity, about 29.42 m/s². Someone experiencing 3 g feels three times their normal weight.
How many m/s² is 1 g?
Exactly 9.80665 m/s² by definition. Local gravity varies slightly, from about 9.78 to 9.83 m/s² depending on latitude and altitude.
Is the g in g-force the same as the g for gram?
No. The g-force g is an acceleration equal to 9.80665 m/s². The gram is a unit of mass. They share a letter but are unrelated quantities.
What is a Gal?
One centimeter per second squared, or 0.01 m/s². It is used mainly in geophysics and seismology to describe ground acceleration, and is named after Galileo.
How do I calculate acceleration from 0 to 100 km/h in a given time?
Divide 27.78 m/s (which is 100 km/h) by the time in seconds. For 6 seconds: 27.78 ÷ 6 = 4.63 m/s², or 0.47 g.
Why can most cars not accelerate faster than about 1 g?
Because tire grip on dry asphalt limits the force that can be transmitted to the road, regardless of engine power. Only vehicles with specialized tires or aerodynamic downforce exceed it meaningfully.
Related converters
- Speed converter, for the velocity that acceleration changes
- Force converter, since force equals mass times acceleration
- All unit converters