Centripetal Force Calculator - G-Force in Turns

A car turning at 60 km/h through a 30-meter roundabout pulls 0.94 g

One number separates a comfortable cruise from a white-knuckle slide: lateral g-force. Enter speed in km/h, turn radius in meters and vehicle mass in kg. The calculator returns centripetal force in Newtons, lateral acceleration in m/s² and g-load. It classifies the turn severity and shows the maximum safe speed for street tires (0.8 g limit) and sport tires (1.2 g limit). The formula is F = mv²/r - force grows with the square of speed, so doubling your speed quadruples the force trying to push you off the road.

Key numbers at a glance

Four scenarios, four very different loads on your tires.

City roundabout

Speed: 30 km/h | Radius: 15 m

G-load: 0.47 g | Force: 6,481 N

Comfortable for passengers, well within tire grip on dry road

Highway curve

Speed: 100 km/h | Radius: 500 m

G-load: 0.16 g | Force: 2,778 N

Barely noticeable - highway curves are engineered for high-speed comfort

Fast roundabout entry

Speed: 60 km/h | Radius: 30 m

G-load: 0.94 g | Force: 13,066 N

Near the grip limit of street tires - on wet road this slides

Track hairpin

Speed: 80 km/h | Radius: 25 m

G-load: 2.01 g | Force: 23,704 N

Only possible with racing slicks or heavy downforce - street tires slide at 1.0 g

The centripetal force formula

Core equation:

F = m * v^2 / r

F = centripetal force (N) | m = mass (kg) | v = speed (m/s) | r = turn radius (m)

G-load: g = v^2 / (r * 9.81) - mass cancels out, so a Miata and a Range Rover pull the same g in the same turn.

Speed must be in m/s. Divide km/h by 3.6 to convert. A car at 60 km/h moves at 16.67 m/s. Force grows with the square of velocity - going from 40 to 80 km/h quadruples the centripetal force.

G-force classification table

G-load range	Classification	Typical scenario	Tire requirement
Below 0.3 g	Very comfortable	City driving, gentle highway curves	Any tire
0.3 - 0.6 g	Normal road turn	Country road, roundabout at moderate speed	All-season OK
0.6 - 0.9 g	Dynamic turn	Spirited driving, track day warm-up	Premium summer
0.9 - 1.3 g	Grip limit	Sport tires on track, racing conditions	Cup 2, AD08R
Above 1.3 g	Beyond street grip	Slick tires, downforce, F1 cornering	Racing slick

Tire grip limits - dry vs wet

Tire type	Max lateral g (dry)	Max lateral g (wet)	Max speed in r=30 m (dry)
Budget all-season	0.70 g	0.40 g	51.7 km/h
Premium summer (PS4, P Zero)	0.95 g	0.60 g	60.3 km/h
Max performance (Cup 2, AD08R)	1.15 g	0.55 g	66.3 km/h
Racing slick	1.50 g	N/A	75.7 km/h

Facts you might not expect

Mass does not affect g-load

An 800 kg Miata and a 2,500 kg Range Rover at the same speed through the same turn feel the exact same g-force. Mass only changes the force in Newtons - heavier cars stress tires more.

Double speed = 4x force

Force grows with the square of velocity. Going from 40 to 80 km/h in the same turn quadruples the centripetal force and g-load. That is why speed kills in corners.

Wet roads cut grip by 40%

Street tires on dry asphalt hold 0.8-1.0 g. On wet pavement that drops to 0.4-0.6 g. The same turn becomes dangerous at a speed that felt safe ten minutes ago.

F1 drivers sustain 5-6 g laterally

Aerodynamic downforce pushes the car into the track, giving tires far more grip than weight alone provides. No road car can match this without wings generating thousands of Newtons.

FAQ - Frequently asked questions

What is centripetal force?

Centripetal force is the net inward force keeping an object on a circular path. For a car in a turn, this force comes from tire friction against the road. Without enough friction, the car slides outward - understeer in FWD cars, oversteer in RWD cars. The force equals F = mv^2/r.

What is the difference between centripetal and centrifugal force?

Centripetal force is real - it is the tire friction pulling the car toward the center of the turn. Centrifugal force is apparent - passengers feel pushed outward because their body wants to continue in a straight line (Newton's first law). In physics, centrifugal force is called a fictitious force that only exists in a rotating reference frame.

Why does vehicle mass not affect the g-load?

G-load equals v^2 / (r * 9.81). Mass is not in the equation. A heavier car needs more force in Newtons to hold the turn, but its tires also press harder into the road (more normal force = more friction). The effects cancel out. G-load depends only on speed and radius.

How do I find the turn radius on a road?

Use Google Maps: zoom in on the turn, right-click the center of the curve to drop a pin, then measure the distance to the outer edge. For roundabouts, the radius is half the central island diameter plus lane width. Typical values: city roundabout 10-20 m, suburban 20-40 m, highway ramp 50-150 m, highway curve 300-1000 m.

What is the maximum safe speed for a given turn?

For street tires on dry pavement (0.8 g limit): v_max = sqrt(0.8 * 9.81 * r) * 3.6 km/h. A 30-meter roundabout: max safe speed is about 55 km/h. A 100-meter highway curve: about 101 km/h. On wet roads, reduce by 30-40%.

Does road banking (camber) affect cornering force?

Yes. A banked road tilts the car inward so gravity provides part of the centripetal force, reducing the load on tires. Highways bank curves at 3-7 degrees. NASCAR tracks bank at 24-33 degrees, allowing much higher cornering speeds. At the ideal banking angle, tires provide zero lateral force.

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