Truck Turning Radius Calculator

Estimating a truck’s turning radius

A truck turning radius calculator estimates how tight a vehicle can turn. Enter the wheelbase in feet and the maximum steering angle in degrees. The tool divides the wheelbase by the sine of the angle.

Picture a truck with its front wheels cranked all the way over. It travels along a circle. A short truck with wheels that turn far makes a small circle. A long truck with a small steering angle makes a big one.

The formula in plain words

Radius = wheelbase ÷ sin(steering angle).

The sine of 30 degrees is 0.5, so a 30° steering angle gives a radius twice the wheelbase. As the angle grows, the sine grows and the radius shrinks.

Worked example: a long-wheelbase truck

A truck has a 20 ft wheelbase and a 30° maximum steering angle.

• Sine of 30°: 0.5
• Radius: 20 ÷ 0.5 = 40 ft

Worked example: a shorter truck with more lock

A truck has a 14 ft wheelbase and a 35° maximum steering angle.

• Sine of 35°: 0.5736
• Radius: 14 ÷ 0.5736 = 24.41 ft

Radius by wheelbase and angle

Wheelbase	Steering angle	Radius
10 ft	30°	20.00 ft
12 ft	35°	20.92 ft
14 ft	35°	24.41 ft
20 ft	30°	40.00 ft
20 ft	40°	31.11 ft
25 ft	30°	50.00 ft

Holding the wheelbase at 20 ft, a 25° lock gives 47.32 ft, 30° gives 40.00 ft, and 45° gives 28.28 ft. A few degrees of steering matters a lot.

What the number represents

The formula is a simplified geometric model of a vehicle on a flat surface. It gives a radius from the geometry of the steering, which is the starting point for planning a turn. It does not include the width of the truck, the cab or bumper that swings out in front, or the body that overhangs the rear axle.

So the real path that a truck sweeps is wider than the number you get here. For access roads, loading docks, and turnarounds, the area needed is the truck’s outer swing and not the geometric radius alone.

How to find the inputs

Wheelbase is on the manufacturer’s spec sheet. You can also measure it from the center of the front wheel to the center of the rear wheel on the side of the truck.

Maximum steering angle is harder. It is often in the technical specs, or it can be measured. Park on level ground, turn the wheel to full lock, and measure the angle of the front tire to the vehicle’s centerline with a protractor or an angle app.

Planning a turn on your site

For a driveway or yard, mark the radius on the ground with a stake and a string. Set the stake at the center of the turn and swing the string to see how much room the circle takes. Then add the width of the truck on the outside of the arc, plus a safety margin. If the circle runs into a fence, a tree, or a building corner, the truck will not make it without backing up.

Wider approaches and rounded corners help trucks that are close to the limit. A wide gate or a corner cut back by a few feet costs little compared with repairing a fence post.

Common mistakes

• Using overall length for wheelbase. Only the axle spacing counts.
• Entering the steering wheel angle instead of the tire angle. The wheel turns many times more than the tires do.
• Treating the radius as the clearance needed. Add the vehicle width and overhang.
• Ignoring trailers. A trailer cuts the corner tighter than the truck.
• Using the result for public road or fire access design without a swept path analysis.

Related calculators

For parking areas, the parking lot striping cost calculator estimates the cost of marking stalls and aisles. A steep approach changes how trucks maneuver, so check slope with the driveway slope calculator.