AtlasCalcsUtility Calculation Suite
Automotive Calculators

Turning Radius Calculator

2026-09-27 6 min

Turn radius and full circle diameter from wheelbase and steer angle (bicycle model).

Turn Radius
13.1 ft
Turn Circle
26.2 ft
Full diameter

Calculator

Wheelbase(in)
in
Steer Angle(deg)
deg
Results update live as you type

Live statistics

Turn Radius

13.1 ft

Turn Circle

26.2 ft

Full diameter

Results

Optimal

Turn Radius

13.1ft

Turn Circle

26.2ft

Full diameter

Planning estimate from standard automotive formulas. Validate with dyno, timeslip or datalog data when precision matters.

Visualizations

Results overview

13.1Turn Radius
26.2Turn Circle

Turn Radius vs. Wheelbase

Turn Radius

13.1ft
060

Formula

Inverse bicycle model: steer angle and wheelbase fix the turn center distance.

Radius = (wheelbase/12) / tan(steer)

Alternative Form

Circle = 2 x radius

Variables

SymbolNameUnitDescription
WBWheelbaseftInches divided by 12
deltaSteer angledegMean road-wheel angle

Explanation

More lock or a shorter wheelbase tightens the circle — the trade firefighters and parking garages care about.

Step-by-Step Calculation

Follow each step to understand how the result is calculated from your inputs.

Step 1

Record the inputs.

Wheelbase:110 in
Steer Angle:35 deg
Result: 2 inputs ready
Step 2

Apply the formula.

Radius = (wheelbase/12) / tan(steer)
Result: Primary result = 13.1 ft
Step 3

Read every derived output.

Turn Radius:13.1 ft
Turn Circle:26.2 ft
Result: Turn Radius = 13.1 ft
Final Answer
13.1

Worked Examples

See how the calculator works with different scenarios.

Scenario

Full-lock parking maneuver.

Inputs

Wheelbase:110 in
Steer:35 deg

Calculation

9.167/tan(35) = 13.1 ft

Result

13.1-ft radius, 26.2-ft circle.

Interpretation

Fits a standard two-lane turnaround with margin.

Understanding Your Result

Your Result: Turn Radius: 13.1 ft

What This Means

Tightest centerline circle the chassis can trace at lock.

Why It Matters

Garage, trail and street design all start from this circle.

Professional Interpretation

Treat the primary result as a planning estimate, then validate on a dyno, at the track, or with logged sensor data. If measured numbers disagree by more than ~10%, re-check inputs (units are the usual culprit) before changing parts.

Recommendations

  • •Double-check units on every input before trusting the result
  • •Compare against the worked example below to sanity-check magnitude
  • •Validate with measured data (dyno, timeslip, datalog) when it matters

Learn — fuel economy, deeply

Lock plus wheelbase draws the smallest circle a car can follow.

1 · Where the gallon goes (energy path)

Engine heat

60–70% lost

Coolant + exhaust carry most energy away. Hybrids recover some via Atkinson cycle + regen.

Driveline

5–15% lost

Transmission, differential, accessories. CVTs and 8–10 speed autos lose less.

Aero drag

∝ v²

Doubles from 55→78 mph. Roof boxes hurt more than trunks.

Rolling + brakes

10–20%

Tires, weight, stops. Regen braking (hybrid/EV) reclaims city braking energy.

4 · Measure like a pro (the 3-tank protocol)

  1. Fill to first click at the same pump, record the odometer (Tank 0).
  2. Drive normally for 2–3 tanks; always refill to first click at the same pump.
  3. MPG = total miles ÷ total gallons across all tanks — averaging kills pump-click noise.
  4. Cross-check with the trip computer; a persistent >10% gap means the computer needs calibration — or the car needs service.
  5. Log with an OBD-II dongle for per-trip MPG if you want to isolate commute vs. highway behavior.

Practical Tips

  • •Use mean steer angle, not just inner
  • •Add overhang for wall-to-wall numbers
  • •Shorter wheelbase turns tighter at equal lock

Common Mistakes

Mixing units (inches with mm, psi with kPa)
Convert every input to the unit shown on its field before calculating.
Trusting a single output blindly
Cross-check with the worked example and, when it matters, a dyno or datalog.

Assumptions

This calculator makes the following assumptions to provide estimates:

Steady-state model: Formulas assume stabilized conditions; transients, heat soak and traction limits are excluded.
Standard factors: Empirical constants (BSFC, VE, drivetrain loss) use typical values — your combination may differ.

Limitations

Be aware of these limitations when using this calculator:

Estimate, not measurement: Predictions carry real-world scatter of roughly ±5–15% depending on the model.
No transient effects: Shift time, wheelspin, spool lag and heat soak are not modeled here.

Frequently Asked Questions

Answers to common questions about this calculator.

Curb-to-curb vs wall-to-wall?
Curb-to-curb tracks the tires; wall-to-wall adds body overhang swing — always larger.
Why does my car need 3-point turns?
Long wheelbase plus limited lock makes a wide circle; both inputs show up directly here.

Related Calculators

Explore more calculators related to this topic.

Related Guides

Deepen your understanding with these educational resources.

Glossary

Technical terms used in mortgage calculations explained in plain language.

MPG
Miles per gallon. Distance travelled per gallon of fuel; higher is better. US gallon = 3.785 L.
L/100 km
Litres consumed per 100 kilometres; lower is better. Standard metric efficiency unit.
MPGe
Miles per gallon-equivalent. EV metric: miles travelled on 33.7 kWh (energy of 1 gal of gasoline).
CAFE
Corporate Average Fuel Economy — US fleet-average efficiency standard enforced by NHTSA.
Rolling resistance
Energy lost deforming tires as they roll. Low-pressure or wide tires raise it.
Aerodynamic drag
Air resistance growing with the square of speed — why highway MPG falls fast above 60 mph.
Hypermiling
Driving techniques (coasting, steady speed, anticipation) that maximise real-world MPG.
OBD-II
On-board diagnostics port. Scanners and dongles read live MPG, fuel trim and fault codes.

Authoritative References

Trusted sources and standards referenced by this calculator.

Applicable Standards

EPA Fuel Economy Testing (40 CFR Part 600)CAFE — Corporate Average Fuel Economy Standards (NHTSA)WLTP — Worldwide Harmonised Light Vehicle Test ProcedureSAE J1321 / J1711 — Fuel consumption test proceduresISO 2575 — Road vehicles symbols & efficiency markings

Was This Calculator Helpful?

Page Information