Load Index Chart

The load index is the number just before the speed letter on your tire’s sidewall — the “94” in 225/45R17 94W. It tells you the maximum weight each tire can carry at its maximum pressure. This page gives the full load index chart, decodes any tire size you type, and checks what load index your vehicle needs.

Reading the tire sidewall

A “P” before the size marks a P-metric passenger tire made to US standards; no prefix means a Euro-metric tire; “LT” means a light truck tire with two load indexes (single and dual fitment) and a load range letter.

Load index chart

Values are the maximum load per tire at the tire’s maximum rated inflation pressure, following the standard load index table used by tire manufacturers. Capacity at lower pressures is lower — follow the pressure on your vehicle’s placard.

Speed ratings

H comes after U, out of alphabetical order, for historical reasons. The speed rating is tested under specific laboratory conditions; it’s not a recommendation to drive at that speed, and a repaired, underinflated or overloaded tire may not be safe at its rated speed.

How to check the load index you need

1. Find the tire placard on the driver’s door jamb or in the owner’s manual; it lists the original tire size, load index and speed rating.
2. Replacement tires should have at least that load index and speed rating.
3. For a check from first principles, find the gross axle weight rating (GAWR) for front and rear axles on the door-jamb certification label.
4. Divide the heavier axle rating by two to get the load per tire.
5. The tire’s capacity must be at least that — the tool above does this and suggests the minimum load index.

Worked example

A car’s door label gives a rear GAWR of 2,425 lb. Dividing by two gives about 1,213 lb per tire. A 94-load-index tire carries 1,477 lb, so it has a comfortable margin; a load index 86 tire (1,168 lb) would be too low. Now take an SUV with a GAWR of 3,900 lb fitted with P-metric tires: each tire must carry 1,950 lb, but P-metric tires on light trucks and SUVs are commonly derated by dividing their capacity by 1.1. A P265/70R17 113T tire carries 1,150 kg (2,535 lb) — 2,305 lb after derating — which is enough.

Extra load, reinforced and LT tires

• Extra load (XL) or reinforced tires carry more load than standard-load tires of the same size, but only when inflated to their higher maximum pressure.
• LT (light truck) tires show two indexes such as 123/120: the first for single fitment, the second for each tire in a dual-wheel set-up.
• LT tires also use a load range letter: C (6-ply rating), D (8-ply rating), E (10-ply rating) and so on; higher letters allow higher pressures and loads.
• Don’t mix load indexes on the same axle, and avoid fitting a lower load index than the vehicle manufacturer specifies — it can affect insurance and roadworthiness in some places.

Tire size maths

Sidewall height = width × aspect ratio ÷ 100. For 225/45R17, that is 225 × 0.45 = 101 mm. Overall diameter = rim diameter + two sidewalls = 17 × 25.4 + 2 × 101 = 634 mm (about 25.0 inches). When changing tire size, many fitters aim to keep the overall diameter within about 3% of the original so that the speedometer, ABS and stability systems read correctly — the decoder shows the diameter for comparing sizes.

Safety note

This page is for information. Tire choice affects braking, handling and safety — follow the vehicle manufacturer’s specification and the advice of a qualified tire fitter, and check tire pressures monthly when the tires are cold.