G-Force Calculator

How to use the G-Force Calculator

1. Under What do you know?, choose one of three modes:
   • Speed change over time for launches and braking, such as a 0–60 mph time.
   • Turn or curve (v²/r) for cars on curves, airplanes in turns and roller coaster loops.
   • Acceleration to convert a value in m/s² or ft/s² straight to g.
2. Enter your numbers. For speed changes, fill in Starting speed, Ending speed, Speed unit (mph, km/h, m/s or ft/s) and Time in seconds. For turns, enter Speed, Turn radius and their units.
3. Press Calculate. The answer is shown in g, m/s² and ft/s², with the steps. Turn mode also shows the load you would actually feel once gravity is included.

G-force formulas

A g-force is an acceleration divided by standard gravity, g₀ = 9.80665 m/s². That value is exact by definition, and because 1 ft is exactly 0.3048 m, it equals about 32.174 ft/s².

Speeds are converted with exact factors: 1 mph = 0.44704 m/s, 1 ft/s = 0.3048 m/s and 1 km/h = 1 ÷ 3.6 m/s.

Example: 0 to 60 mph in 6.0 seconds

1. Convert the speed: 60 mph × 0.44704 = 26.8224 m/s (or 88 ft/s).
2. Average acceleration: 26.8224 ÷ 6.0 = 4.4704 m/s² (88 ÷ 6 = 14.67 ft/s²).
3. Divide by standard gravity: 4.4704 ÷ 9.80665 = 0.456 g.

Braking from 60 mph to a stop in 3.0 seconds is the same calculation in reverse: −26.8224 ÷ 3 = −8.9408 m/s², or −0.912 g. The minus sign means the car is slowing down.

Example: a highway curve

A car takes a curve with a 300-foot radius at 45 mph. At 45 mph the car moves 66 ft/s, so a = 66² ÷ 300 = 14.52 ft/s², which is 0.451 g pushing sideways toward the center of the curve. Combined with gravity on a flat road, occupants feel √(1 + 0.451²) ≈ 1.097 g in total. A road banked at about 24.3° would line that combined force up with the seat, the same reason airplanes bank in turns.

Example: airplanes in a turn

OpenStax University Physics works an example of a jet flying at 134.1 m/s (about 300 mph) and finds that a turn radius of about 1.835 km gives a centripetal acceleration of 1 g. Entering 134.1 m/s and 1,835 m in turn mode gives 0.999 g.

For pilots, the felt load includes gravity. The FAA notes that in a 60° banked turn in level, coordinated flight, the load factor is 2 G's. The calculator reproduces this: at 300 mph on a 3,474-foot radius, the sideways acceleration is 1.732 g, the coordinated bank angle is 60°, and the felt load is √(1 + 1.732²) = 2.0 g.

Roller coaster loops

At the bottom of a vertical loop, the track has to supply the turning force and hold riders up against gravity, so riders feel n + 1 g. At the top, gravity already pulls toward the center, so they feel n − 1 g. As an illustration, a car moving 45 mph through the bottom of a curve with a 70-foot radius has n = 66² ÷ 70 ÷ 32.174 ≈ 1.934, so riders feel about 2.93 g. Use the speed and radius at each point of the ride, because both change around a real loop.

How to read the result

• Positive g in speed mode means speeding up; negative means slowing down.
• In turn mode the headline number is the sideways (centripetal) part only. The extra rows add gravity for a flat turn and for the bottom and top of a loop.
• 1 g equals the pull of standard gravity: 9.80665 m/s² or about 32.174 ft/s². Standing still, you already feel 1 g.

Assumptions and limitations

• Speed-change results are averages over the time you enter. Real launches and stops are uneven, so the peak g-force is higher than the average.
• Turn results assume a steady speed on a circular path of the radius you enter.
• The calculator uses standard gravity, a fixed conventional value, for every conversion.
• Results are rounded to three decimals in g and four in m/s² and ft/s².

Note: These are physics estimates for learning and planning. They are not safety ratings for vehicles, rides or aircraft, and they say nothing about how much g-force a particular person can tolerate.

Common mistakes

• Forgetting to convert units. Dividing 60 mph by 6 seconds gives 10 "mph per second," not m/s². Convert speeds to m/s or ft/s first; the calculator does this for you.
• Using the diameter as the radius. The radius of a 600-foot-wide circle is 300 feet.
• Treating v²/r as the total felt load. In a flat turn, gravity adds a second 1 g at a right angle, so the total is √(1 + n²).
• Mixing standard gravity values. Using 9.8 m/s² instead of 9.80665 m/s² changes results only slightly (about 0.07%), but use 9.80665 to match official conversions.

Interested in other science math? Try the Exponential Decay Calculator for half-life problems, or the Area of a Sector Calculator for arcs and curved paths.

Formulas and content last reviewed on October 13, 2026. Last updated October 13, 2026. Results are estimates for general information only. Spotted a problem? Tell us and we will check it.