Litres consumed per 100 kilometres; lower is better. Standard metric efficiency unit.

Energy lost deforming tires as they roll. Low-pressure or wide tires raise it.

Automotive Calculators

Roll Center Calculator

2026-09-27 6 min

Front roll-center height and jacking proxy from control-arm angles and track width.

Roll Center Height: 2.10 in
Jacking Proxy: 2.10 in; Equals RC height (relative index)

Calculator

Upper Arm Angle(deg)

deg

Lower Arm Angle(deg)

deg

Track Width(in)

Results update live as you type

Live statistics

Roll Center Height

2.10 in

Jacking Proxy

2.10 in

Equals RC height (relative index)

Results

Optimal

Roll Center Height

2.10in

Jacking Proxy

2.10in

Equals RC height (relative index)

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

Visualizations

Results overview

2.1Roll Center Height

2.1Jacking Proxy

Roll Center Height vs. Upper Arm Angle

Roll Center Height

2.1in

012

Formula

Instant-center geometry reduced to an arm-angle index: converging arms raise the roll center.

RC height = (track/2) x tan((upper - lower)/2)

Alternative Form

Jacking force scales with RC height

Variables

Symbol	Name	Unit	Description
RC	Roll center height	in	Roll axis height at this axle
track	Track width	in	Tire-center to tire-center

Explanation

A high roll center jacks the body up in corners and skips over bumps; a low one lets the body roll more but ride calmer.

Step-by-Step Calculation

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

Step 1

Record the inputs.

Upper Arm Angle:10 deg

Lower Arm Angle:2 deg

Track Width:60 in

Result: 3 inputs ready

Step 2

Apply the formula.

RC height = (track/2) x tan((upper - lower)/2)

Result: Primary result = 2.10 in

Step 3

Read every derived output.

Roll Center Height:2.10 in

Jacking Proxy:2.10 in

Result: Roll Center Height = 2.10 in

Final Answer

2.10

Worked Examples

See how the calculator works with different scenarios.

Scenario

Double-wishbone front end.

Inputs

Upper:10 deg

Lower:2 deg

Track:60 in

Calculation

30 x tan(4 deg) = 2.10 in

Result

2.10-in roll center.

Interpretation

Low, well-behaved RC for a street/track car.

Understanding Your Result

Your Result: Roll Center Height: 2.10 in

What This Means

Height of the axle roll axis from simplified arm angles.

Why It Matters

Sets jacking behavior and how much roll the springs and bars must control.

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

Control-arm angles locate the point the body rolls about.

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)

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

Practical Tips

•Equal arm angles give a ground-level RC
•Raising the upper-arm angle raises the RC
•Compare front vs rear RC for the roll-axis slope

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.

Is a higher roll center better?

Not always — high RCs reduce body roll but add jacking and camber headaches; moderate heights are friendliest.

Is this exact geometry?

No — a simplified arm-angle index for planning. Full instant-center CAD work refines it.

Related Calculators

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Related Guides

Deepen your understanding with these educational resources.

Automotive Guides

Build planning, measurement protocol and validation how-tos

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.

EPA — FuelEconomy.gov DOE — Fuel-Efficient Driving Tips NHTSA — Driving Safety & Efficiency SAE International — Fuel Economy Standards Consumer Reports — MPG Truth IRS — Standard Mileage Rates

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

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Page Information

Last Updated:

2026-09-27

Version:

2.0.0

References:

License:

Free to use for educational and professional purposes.