What Is Turning Radius?
Turning radius is the smallest circular space a vehicle can turn within.
In simple terms, it answers this question:
How wide does the road or open space need to be for my vehicle to turn around without backing up?
Most vehicles publish a turning circle number, but those numbers are often simplified. This calculator goes deeper and gives you two useful measurements.
Curb-to-Curb vs Wall-to-Wall Turning Diameter
The calculator provides two results because vehicles do not just turn on tires alone.
Curb-to-Curb Turning Diameter
- Measures the path of the outer front tire
- Assumes no obstacles like walls or parked cars
- Commonly used in vehicle specs
This tells you how tight the vehicle can turn on open pavement.
Wall-to-Wall Turning Diameter
- Measures the outer front bumper corner
- Includes front overhang
- Represents real-world conditions like garages or narrow streets
This is the more realistic number when space is tight.
Why Turning Radius Matters
Turning radius affects more than convenience.
- City driving: Narrow streets and U-turns
- Parking: Garages, ramps, and tight lots
- Driveway design: Residential and commercial layouts
- Fleet planning: Trucks, vans, and service vehicles
- Safety: Reduced need for risky multi-point turns
A few extra feet can be the difference between a smooth turn and backing into traffic.
How This Turning Radius Calculator Works
This calculator uses Ackermann steering geometry, which models how real vehicles steer.
Instead of guessing, it calculates the turning path based on physical measurements.
Inputs Explained
1. Measurement System
- Imperial: inches and feet
- Metric: millimeters and meters
Choose the system that matches your vehicle data.
2. Wheelbase
- Distance between front and rear axles
- Longer wheelbases increase turning diameter
3. Track Width
- Distance between left and right wheels
- Wider vehicles need more turning space
4. Maximum Steering Angle
- Maximum angle of the inner front wheel
- Most vehicles fall between 30° and 45°
5. Front Overhang
- Distance from front axle to bumper
- Only affects wall-to-wall turning diameter
The Math (Explained Simply)
You do not need to do this by hand, but understanding the logic helps.
- The calculator converts steering angle to radians
- It finds the pivot point of the rear axle
- It measures how far the outer front wheel travels
- It adds the bumper overhang for real-world clearance
- It doubles the radius to get full turning diameter
This approach mirrors how vehicles actually behave when turning.
Understanding the Results
After clicking Calculate Radius, you will see:
- Curb-to-Curb Diameter
- Wall-to-Wall Diameter
- A short real-world analysis
Example Interpretations
- Under 34 ft (10.4 m): Very tight turning, easy U-turns
- 34–38 ft (10.4–11.6 m): Average passenger vehicle
- 38–45 ft (11.6–13.7 m): Large SUVs or trucks
- Over 45 ft (13.7 m): Long wheelbase or commercial vehicles
The calculator also explains whether U-turns are likely possible on standard roads.
Imperial vs Metric Output
The calculator automatically converts results:
- Imperial: Inches in, feet out
- Metric: Millimeters in, meters out
This avoids confusion and keeps results practical.
Switching units clears the inputs to prevent scaling mistakes.
Common Mistakes to Avoid
- Entering wheelbase instead of overall length
- Using unrealistic steering angles above 60°
- Ignoring front overhang for garages or walls
- Comparing curb-to-curb numbers to wall-to-wall spaces
Always match the result type to your real situation.
Who Should Use This Calculator?
This tool is useful for:
- Drivers comparing vehicle maneuverability
- Builders designing driveways or parking areas
- Engineers and students learning vehicle geometry
- Fleet managers planning vehicle access routes
- Off-road and custom vehicle builders
If space matters, this calculator helps you plan with confidence.
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