Decode the load index and speed rating molded on your tyre — the number for the weight each tire can carry, the letter for its top speed — in kilograms and pounds and in km/h and mph.
Most load-index charts are gated or copyrighted PDFs, kg-only or lb-only, and never connect to the weight you actually need to carry. This one is computed live from the standard formula, decodes the full sidewall code (load index and speed rating together), shows both kg and lb, and works the other way: enter the load you need per tire and get the minimum load index.
Required load per tire = the heaviest axle weight divided by the tires on that axle. Size your rig with the towing capacity calculator first if you are not sure of the axle figure.
Load values are computed from the standard load-index formula and match the published ISO load-index values to within normal rounding. Speed figures are the standard ISO speed symbols. The exact maximum load and pressure for your tire are molded on its own sidewall — always fit a tire that meets or beats the load index and speed rating on your vehicle’s placard.
This load index chart is computed, not copied: each row is the maximum load per tire worked out from the standard formula below, shown in both kilograms and pounds. Tap a heading to sort, and tap a row to load it into the decoder. Passenger cars usually sit between load index 75 and 100; vans, light trucks and trailers run higher.
Tyre load index to maximum load per tire — computed from the standard formula.
Load index ▲
Max load (kg)
Max load (lb)
kg = 45 × 10^(LI / 80) · lb = kg × 2.20462
Spot-checks against the standard: load index 91 ≈ 615 kg (1,356 lb), 100 = 800 kg (1,764 lb), 109 ≈ 1,030 kg (2,271 lb). Because the curve is smooth, every increase of about three index points is roughly a 10% jump in capacity.
Tyre speed rating chart (km/h and mph)
The speed rating is the letter at the end of the service description. It is the maximum speed the tire is certified for when correctly loaded and inflated — not a target. The common road ratings run from S and T up through H, V, W and Y; low-speed symbols appear on some trailer and off-road tyres. Note that I, O and X are not used, and a Z or ZR in the size marks a high-speed tire (a modern ZR tyre is also marked W or Y in the service description).
Tire speed rating letter to maximum speed in km/h and mph (standard ISO speed symbols).
Symbol
Max km/h
Max mph
Typical use
Load index and speed rating together
On the tyre the two appear as one short code — the service description — right after the size. In 225/45R17 91V, the 91 is the load index (about 615 kg per tire) and the V is the speed rating (up to 240 km/h / 149 mph). The same code can be written on its own as just 91V. The decoder above accepts either form and splits out both halves with their values in kg, lb, km/h and mph.
What load index do I need?
Work from weight, not guesswork. Take the heaviest axle weight, divide by the number of tires on that axle, and that is the load each tire must carry. Then pick a tire whose load index meets or beats it. The reverse mode above does the lookup — enter the required load per tire and it returns the minimum load index. As a hard rule, never fit a tyre with a lower load index than the one on your door-jamb placard.
XL / Extra Load, P-metric vs LT, and dual ratings
A few markings change how you read the number:
XL or Extra Load — a reinforced passenger tyre with a higher load index than the standard version of the same size, reached at a higher inflation pressure. Read its load index the same way; it is simply a larger number.
P-metric vs LT — passenger (P) tyres used on a light truck or SUV are de-rated, typically to about 91% of their marked capacity, because the standards bodies assume heavier, less forgiving use. An LT (light-truck) tyre carries its full marked load index.
Dual load index (e.g. 108/104) — the first number is the capacity as a single tire, the second the lower capacity when mounted as a dual pair, kept lower on purpose for safety if one of the pair fails.
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Frequently asked questions
What does the load index on a tyre mean?
The load index is the number just before the speed letter in the service description, like the 91 in 91V. It is a code for the maximum weight one tire can carry at its rated pressure — a higher number means more capacity. Load index 91 is about 615 kg (1,356 lb) per tire and 100 is 800 kg (1,764 lb). It is not the weight in pounds itself; you look it up, and this chart computes it from the standard formula so there is no gated PDF to hunt down.
How do I read a service description like 91V or 225/45R17 91V?
Split it into the load index (the number) and the speed rating (the letter). In 91V, 91 is the load index (~615 kg per tire) and V is the speed rating (up to 240 km/h / 149 mph). In 225/45R17 91V the 225/45R17 is the size and 91V is the service description. Paste either form into the decoder above to get the load per tire in kg and lb and the speed in km/h and mph.
What load index do I need for my vehicle?
Take the heaviest axle weight, divide by the number of tires on that axle to get the load each tire must carry, then choose a tyre whose load index meets or beats it. The reverse mode above does this — enter the required load per tire and it returns the minimum load index. Never fit a tire with a lower load index than the original on your placard.
What does a dual load index like 108/104 mean?
Light-truck and some trailer tyres can run as singles or in dual pairs. The first number is the load index as a single, the second the lower index used when two are mounted together on one hub. The dual figure is lower on purpose so the axle stays safe if a tire in the pair fails. For 108/104 that is roughly 1,000 kg as a single and about 900 kg per tire in a dual set.
Is the load index the same as the load range?
No — this trips a lot of people up. The load index is a number giving the exact maximum weight per tire. The load range is a letter (B, C, D, E, F) describing how the tyre is built and the pressure it is rated for. Two tires with the same load range can have different load indexes, so the capacity number always comes from the load index. The load range & ply rating chart covers the letter side.
Does a higher speed rating mean a better tyre?
Not by itself. A higher speed rating (say V or W instead of T) usually means a stiffer sidewall and firmer handling, but it can ride harder and wear faster, and many capable off-road and trailer tyres carry a low rating like L or Q on purpose. Match at least the rating on your placard; going much higher is a handling and cost choice, not a safety requirement.