Understanding Acceleration Units: m/s2, g, ft/s2 and the Gal
By the Super Simple Digital Tools Team · Updated June 2026
Acceleration is simply how fast velocity changes, and its units always combine a distance unit with time squared, such as metres per second, per second. That structure is why every acceleration unit can be converted into any other through a clean multiplication factor: they all describe the same quantity at different scales. Once you internalise that m/s2, ft/s2, g, and the Gal are just different rulers for the same thing, conversion stops feeling mysterious and becomes pure bookkeeping.
The international reference point is standard gravity, fixed at exactly 9.80665 m/s2 and written as g. It represents the pull you feel standing still on Earth. Expressing acceleration in g is intuitive because it tells you immediately how the force compares to your own body weight: pulling 2 g means you feel twice as heavy. This is why g-force dominates aviation, automotive, and theme-park discussions, even though the underlying physics is always reducible to plain m/s2.
The other common units serve specific communities. Feet per second squared keeps imperial calculations consistent in parts of engineering and US aviation, where 1 ft/s2 equals exactly 0.3048 m/s2. The Gal, named after Galileo and equal to 1 cm/s2, lives at the opposite end of the scale: it is the working unit of gravimetry and seismology, where the interesting signals, like buried density anomalies or distant earthquakes, are tiny fractions of a Gal, so scientists often drop to milligal.
To convert by hand, push everything through m/s2 as a hub. Multiply g by 9.80665 to reach m/s2; multiply ft/s2 by 0.3048; multiply Gal by 0.01. Then reverse the relevant factor to land on your target unit. Going from g to ft/s2, for instance, means 9.80665 divided by 0.3048, giving the familiar 32.174 ft/s2 for one g. This tool automates exactly that chain so you avoid sign and direction mistakes.
Putting numbers to everyday experience makes the units concrete. A brisk sports car reaching 60 mph in about three seconds averages roughly 0.9 g; a strong roller coaster peaks near 4 to 5 g; a fighter pilot in a hard turn may sustain around 9 g with the help of a g-suit; and an untrained person typically nears blackout around 5 g. Seen in m/s2, those are about 9, 44, 88, and 49 respectively, which shows just how much friendlier g-force is for grasping intense motion at a glance.
- Remember the single anchor: 1 g = 9.80665 m/s2 exactly. Almost every acceleration conversion you need flows from that one number.
- When a car or coaster figure is quoted in g, multiply by about 9.81 for a quick mental m/s2 estimate, then use the tool for the precise value.
- For seismic or gravity-survey data, switch to Gal or milligal; 1 mGal is one millionth of standard gravity, the resolution that field instruments work at.
- If you need engineering-grade results, replace standard g with your local gravitational acceleration, which can differ by up to about 0.5 percent between the equator and the poles.