Turning radius and turning circle
Wheelbase and steering angle set how tightly a vehicle can turn. This gives both the simplified centreline radius engineers use for quick estimates, and the curb-to-curb figure — the one manufacturers actually publish — which accounts for track width and the outer wheel's wider path.
| Steering angle | Turning circle |
|---|---|
| 25° | 47.8 ft |
| 30° | 41.2 ft |
| 35° | 36.5 ft |
| 40° | 33.2 ft |
| 45° | 30.6 ft |
Getting a number you can act on
- 01Find the vehicle's wheelbase
The distance between front and rear axle centres, in a manufacturer's specification sheet or measured directly.
- 02Find or estimate the average steering angle at full lock
The inner and outer front wheels turn to slightly different angles at full lock (Ackermann geometry); the average of the two is what this simplified model uses.
- 03Enter front track width
The distance between the centres of the two front tires — this is what separates the simplified centreline radius from the real curb-to-curb figure.
- 04Read turning circle as the practical figure
This is the diameter — twice the curb-to-curb radius — and it is the number that actually tells you whether a U-turn fits in a given road width.
What the calculator is actually doing
Nothing here is proprietary. If you would rather check it by hand, or explain it to someone at a counter, these are the same expressions the tool evaluates.
R = wheelbase ÷ tan(steering angle)The simplified bicycle-model approximation, treating the vehicle as a single two-wheeled bicycle rather than modelling each front wheel individually.
R = wheelbase ÷ sin(steering angle) + track width ÷ 2Tracks the outer front wheel's actual path — the figure manufacturers publish — adding half the track width because the outer tire sits further out than the vehicle's centreline.
Why sin and tan give different answers
Both formulas describe the same turning vehicle, but they answer slightly different questions. The centreline (tan) version asks where the midpoint between the front wheels traces its path — a simplification useful for quick estimates and for path-planning algorithms.
The curb-to-curb (sin) version specifically tracks the outer front wheel, which is the widest point the vehicle actually sweeps and therefore the figure that determines whether a turn physically fits. Because sine is always greater than tangent for the same angle under 90 degrees, the sin-based curb-to-curb radius comes out larger than the simplified centreline figure — a real and expected difference, not a rounding error.
Manufacturers publish curb-to-curb figures because that is what matters for parking and manoeuvring. The centreline figure is more of an engineering and robotics convenience, used in path-planning models where the exact width of the vehicle is handled separately.
Turning Radius & Turning Circle Calculator FAQ
How do I calculate turning radius?+
Divide the wheelbase by the tangent of the average steering angle for a simplified centreline estimate, or by the sine of the steering angle plus half the track width for the curb-to-curb figure manufacturers publish.
What is the difference between turning radius and turning circle?+
Turning radius is the distance from the centre of the turn to the outer wheel's path. Turning circle is the full diameter — twice the radius — and is usually the figure quoted for practical purposes like fitting a U-turn.
Why does track width matter for turning radius?+
Because the outer wheel — the one that determines how much room a turn actually needs — sits half the track width away from the vehicle's centreline, which the curb-to-curb formula accounts for and the simplified centreline formula does not.
Does wheelbase or track width matter more for turning radius?+
Wheelbase has the larger effect — it appears directly in both formulas as the primary distance, while track width only contributes half its value as an addition to the curb-to-curb figure.
Standards and references behind these figures
The arithmetic on this page is fixed, but the boundaries and conventions around it come from published standards and manufacturer guidance. These are the documents they come from, so you can check them rather than take them on trust.
01Ford Performance — dynamometer testing and engine performance tech tipsManufacturer guidance on dyno correction and how quoted power figures are arrived at.↗02The Tire and Rim Association — standards filing (NHTSA docket)TRA has been the US standardising body for tire and rim interchangeability since 1903; this filing sets out dimensional practice.↗The wheel is only half the fitment. This calculates where the rim sits. The tire mounted on it reaches further out and further in than the rim does, and that rubber is what makes contact. Check the actual gaps at the strut and inside the fender, at full steering lock and full suspension compression, before ordering.