325/45R24 vs 315/45R24 tire size comparison

Change either size and everything below updates.

Start from your car make, model, year
Current tire size
/R
xR
New tire size
/R
xR

Width in mm · aspect = sidewall height as a % of width · rim in inches

Flotation (LT) sizes, all in inches: overall diameter × section width, then rim

325/45R24: 35.52″ (902 mm) tall, 12.80″ (325 mm) wide, sidewall 5.76″ (146 mm) — 568 revolutions per mile.

Well within tolerance

−1.00% diameter

The overall diameter changes by less than 1.5%, so speedometer error is negligible and ride height barely moves.

  • 10 mm narrower: check the tire is approved for your rim width.

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Measurement325/45R24315/45R24Diff%
Overall diameter35.52″902 mm35.16″893 mm−0.35″−1.0%
Section width325.0 mm315.0 mm−10.0 mm−3.1%
Sidewall height146.3 mm141.8 mm−4.5 mm−3.1%
Rim diameter24″24″0″0.0%
Circumference111.58″2834 mm110.46″2806 mm−1.11″−1.0%
Revolutions per mileturns per distance; drives the odometer568353 /km574356 /km+6+1.0%
Ride height change——−0.18″ −4.5 mm

Speedometer reading

Speedo shows
60mph
97 km/h
Actual speed
59.4mph
96 km/h

Overlay

325/45R24315/45R24

How to use the tire size calculator

Put your current tire size — width, aspect ratio and rim diameter — into the first form, then your desired size into the second. You’ll get the difference between the new and the old size, plus the speedometer reading difference and your actual speed on the new set. Both metric and flotation (LT inch) sizes are supported.

The calculator helps you decide whether a set of tires and wheels will fit your car. To compare tires by brand and model instead, use our tire comparison tool; to look up factory sizes, browse by car make.

Changing wheels too? The wheel offset calculator shows how far a new wheel width and offset move the tire toward the suspension and the fender.

Reading a tire size

225/45R17
225
Section width in millimetres
45
Aspect ratio — sidewall height as a % of width
R
Radial construction
17
Rim diameter in inches

Full guide to the tire sidewall →