Next to the load index on a tire's sidewall sits a single letter: the speed symbol. It says how fast the tire has been tested to run while carrying its rated load. For most family cars it is a T, H or V, and for fast cars it is W or Y. This calculator converts the symbol into kilometres and miles per hour, and finds the lowest symbol that covers the speed you need — useful when you are comparing replacements or checking a different size.
How to use the tire speed rating calculator
- Choose the direction: convert a symbol to a speed, or find the minimum symbol for a speed.
- Pick the symbol shown after the load index (e.g. the H in 91H), or enter the top speed in mph or km/h.
- Read the rated speed in km/h and mph, and the minimum symbol.
The number before the letter is the load index — use the tire load index calculator for it. To see how fast your car can go with its gearing, see the top speed calculator.
Speed rating formula and table
Minimum symbol = the lowest letter whose speed is at or above the speed you need
- Speed symbols run from L (120 km/h) through H (210) and V (240) to Y (300)
- The letters are not in alphabetical order: H sits between U and V
Worked example: 225/45R17 91V
- Speed symbol: V = 240 km/h.
- In miles per hour: 240 ÷ 1.609344 = 149 mph.
- Reverse: a car with a 125 mph top speed is 201 km/h; U (200 km/h) falls just short, so the minimum is H (210 km/h).
All speed symbols
Values from the speed symbol table in this site's data folder; mph is calculated.
| Speed symbol | Maximum speed | In mph |
|---|---|---|
| L | 120 km/h | 75 mph |
| M | 130 km/h | 81 mph |
| N | 140 km/h | 87 mph |
| P | 150 km/h | 93 mph |
| Q | 160 km/h | 99 mph |
| R | 170 km/h | 106 mph |
| S | 180 km/h | 112 mph |
| T | 190 km/h | 118 mph |
| U | 200 km/h | 124 mph |
| H | 210 km/h | 130 mph |
| V | 240 km/h | 149 mph |
| W | 270 km/h | 168 mph |
| Y | 300 km/h | 186 mph |
Choosing a speed rating
The rule for replacements is to match or exceed the rating your vehicle manufacturer specifies, which is on the door-jamb label. Going higher is permitted, but a higher rating often means a firmer ride and a shorter-lasting tread compound. Going lower reduces the speed margin of the tire and can affect handling and insurance, and some manufacturers and tire makers say that the vehicle's safe top speed becomes limited to the lowest rating on any wheel.
In practice, the speed ratings on ordinary road cars exceed any legal limit by a big margin, and that is deliberate: the test speed leaves a margin for heat, load and wear. A T rating covers 118 mph, H covers 130 mph and V covers 149 mph. What matters more day to day is the load index, inflation pressure and tire age, which determine whether a tire can handle sustained loads at highway speed.
If you change tire size, also check that the new tire has the same or a higher rating and load index. The tire size comparison calculator covers dimensions, and the tire load index calculator covers capacity.
Sources
Speed symbols and their maximum speeds (L 120, M 130, N 140, P 150, Q 160, R 170, S 180, T 190, U 200, H 210, V 240, W 270, Y 300 km/h) are from the tire-industry speed symbol table published in the Wikipedia article “Tire code” and in Hankook's tire guide (the two differ only on the A-series symbols and on P/Q, where the Wikipedia values are used); the table is stored in data/tire-speed-ratings.csv. Miles per hour are calculated with 1 mile = 1.609344 km.
Frequently asked questions
What does the letter after the load index mean?
It is the speed symbol: the maximum speed the tire is rated for while carrying its rated load under test conditions. H is 210 km/h (130 mph), V is 240 km/h (149 mph), T is 190 km/h (118 mph).
Do I need a tire rated for my car’s top speed?
The rating must be at least what the vehicle manufacturer specifies, and it is wise to meet or exceed the car’s top speed. A higher rating also usually means a more responsive tire, often with a shorter tread life.
Can I mix speed ratings?
Tire makers recommend the same rating on all four wheels. If ratings are mixed, the lowest rating limits the vehicle’s safe speed, and the higher-rated tires usually go on the rear.
What are (W) and (Y), and Z?
Brackets mean the tire can exceed the speed of that symbol, tested under the maker’s own conditions. Z indicates a rating above 240 km/h (149 mph).
Does the rating mean it is safe to drive that fast?
No. It is a test speed under rated load and correct pressure, not a driving recommendation; always obey speed limits and adapt to conditions.