Acceleration converter

How to convert g-force to m/s²

Multiply g by 9.80665, the exact value of standard gravity in m/s². So 2 g = 19.6133 m/s² and 0.5 g = 4.903325 m/s². Divide by 9.80665 to go from m/s² to g. The factor holds for any g-force figure: car tests, rides or accelerometer logs.

Acceleration unit factors

Each unit is a fixed number of meters per second squared, as listed in NIST's acceleration conversion tables:

• Standard gravity (g): 9.80665 m/s², adopted by the 3rd General Conference on Weights and Measures in 1901.
• Foot per second squared (ft/s²): 0.3048 m/s², because the international foot is 0.3048 m.
• Gal (galileo): 1 cm/s², or 0.01 m/s².

To convert between any two, multiply by the factor of the unit you have and divide by the factor of the unit you want. For 1 g in ft/s²: 9.80665 ÷ 0.3048 = 32.1740485564… ft/s², a repeating decimal.

Acceleration conversion chart

The ft/s² value is rounded to six decimal places. Every other row is exact.

How to work out g-force from a 0–60 time

Average acceleration is the speed gained divided by the time taken. Put the speed in m/s, divide by the seconds, then divide by 9.80665 to get g:

1. 0 to 60 mph is a gain of 60 × 0.44704 = 26.8224 m/s.
2. In 3 seconds that averages 26.8224 ÷ 3 = 8.9408 m/s².
3. In g: 8.9408 ÷ 9.80665 ≈ 0.911708 g.

The same run in 4 seconds averages 6.7056 m/s², about 0.68 g. A 0–60 time gives only the average: the peak during the run is higher unless the push was perfectly steady.

Braking works the same way with a minus sign. Stopping from 60 mph in 4 seconds averages −6.7056 m/s², about −0.68 g. The sign shows the acceleration points against the direction of travel.

The speed converter turns km/h or knots into m/s. When distance is part of the problem, the kinematics calculator solves the constant-acceleration (SUVAT) equations.

Standard gravity is not local gravity

The g in g-force is a fixed reference, not the gravity where you stand. Real free-fall acceleration is about 9.780 m/s² at the equator and 9.832 m/s² at the poles, because Earth spins and bulges at the equator.

Measured against standard gravity, those are about 0.997282 g and 1.002585 g. The familiar 9.81 m/s² is 9.80665 rounded and sits 0.034% high. Rounding g to 10 m/s² makes every answer 1.97% high.

Gal and milligal

The gal is 1 cm/s², named after Galileo, and its symbol Gal has nothing to do with gallons. 100 Gal is 1 m/s², about 0.101972 g.

Earth's surface gravity is about 980 Gal, so gravity surveys measure local differences in milligals. One mGal is 0.00001 m/s², about a millionth of g.

Common mistakes

• Treating 32.174 ft/s² as exact. It is rounded: 32.174 × 0.3048 = 9.8066352 m/s², not 9.80665.
• Converting a speed to g. 60 mph is a speed. It becomes an acceleration only after the change in speed is divided by a time.
• Calling g-force a force. A g figure is an acceleration. Newtons also need a mass, through F = ma; the force converter handles force units.

Typing g-force, milligals and negative values

• A unit typed after the number is read as that unit: 2 g-force, 2 gee and 9.81 m/s^2 are all accepted.
• There is no milligal unit, so enter milligals as a fraction of a gal: 25 mGal is 25/1000 Gal.
• Negative values keep their sign in every unit, so a braking figure stays negative.