Load index and speed rating

The load index is the number that identifies a tire’s rated load capacity; the speed symbol is the letter that identifies its rated speed category. In a marking such as 225/65R17 95H, 95 is the load index and H is the speed symbol. When replacing tires, meet or exceed the original tire’s load index and speed rating, and follow the vehicle placard and owner’s manual. A tire size that looks right can still have the wrong capacity or rating.

For a simple comparison, load index 95 corresponds to 1,521 pounds per tire, while H corresponds to a 130 mph speed category. These ratings are assigned under specified conditions; they are not a recommendation to carry that load or drive at that speed. Actual selection also depends on tire type, inflation pressure, wheel, vehicle requirements and intended service. See how to read a tire size for the rest of the sidewall marking.

The load index is a code, not a weight measurement: index 100 does not mean 1,000 pounds. Each index maps to a maximum load per tire in a standardized table. The capacity is tied to prescribed test and inflation conditions, so the number is useful for comparing ratings but does not by itself tell you the load a tire can carry at every pressure.

The table lists examples commonly encountered on passenger and light-truck tires. It is a quick reference, not a complete index table. Some indexes are skipped in common fitments, and service type matters. In particular, do not use a passenger-tire table to interpret an LT tire’s load range or assume that identical-looking indexes always have identical application requirements.

The speed symbol is the letter immediately after the load index. It identifies a speed category established in controlled testing with the tire properly loaded and inflated. It does not mean a tire should be driven at that speed on public roads, and it does not override speed limits, vehicle limits, weather, load, tire condition or other safe-driving requirements.

Common symbols include S, T and H on passenger tires, and Q or R on some light-truck and winter applications. Higher categories include V, W and Y. The chart gives familiar categories; symbols below or between these examples also exist. The tire maker’s specifications are the authority for a particular model and service type.

A passenger tire marked Standard Load is designed for its rated service within the applicable standard load and inflation limits. An Extra Load tire, often marked XL or sometimes Reinforced, is built to carry more load than a standard-load tire of the same size when used at the higher pressure specified for that load. The XL marking does not automatically mean the tire is suitable for every heavier vehicle or that it always carries more load at the vehicle’s placard pressure.

A tire’s sidewall maximum pressure is not a substitute for the vehicle maker’s recommended cold pressure. Follow the placard and manual, and have a tire professional confirm pressure when a replacement specification or vehicle use requires it. Passenger tires used on certain trucks may require a load adjustment; vehicle and tire-maker guidance should determine the appropriate capacity. For light trucks, also distinguish an LT tire’s load range and single/dual service ratings from a passenger tire’s XL designation. See LT vs P-metric tires for those differences.

Load index and load range are not interchangeable labels. Load range describes a tire’s construction and pressure category in certain tire types, while the load index is a numeric capacity code used on many passenger tires. An LT tire may show two load indexes, such as 121/118; the first applies to single-tire use and the second to dual-tire use. Read the full service description and tire specifications rather than comparing only one number.

As a replacement baseline, never go below the original load index or speed rating. A lower load index can reduce the tire’s capacity below what the vehicle was designed to carry. A lower speed symbol means the tire has a lower tested speed category. The original rating is not a substitute for checking the placard and manual, especially if the vehicle has different front and rear sizes, carries heavy loads, or has approved alternate fitments.

Some winter-tire guidance permits a lower speed category for certain vehicles when the driver observes a speed restriction, but that is a specific exception to verify in the vehicle and tire manufacturers’ instructions. Do not apply it as a general rule to ordinary replacements. When unsure, select a tire that meets or exceeds the original rating and ask a qualified tire professional to confirm fitment and pressure.

A replacement can have the same overall diameter and still fail the load requirement. For example, changing from 225/65R17 95H to a tire with an otherwise compatible size but a lower index would not be validated by a size calculator. The calculator compares nominal dimensions and their effects; it cannot confirm load capacity, speed category or vehicle approval. For a worked size comparison, open the tire size calculator with 225/65R17 and 235/60R18 prefilled, then separately verify the service descriptions of the exact tire models you are considering.

Before buying, compare the complete sidewall service description, confirm Standard Load or XL as appropriate, verify the exact model’s load and speed information, and check the vehicle placard and manual. The U.S. tire standard sets performance requirements for new tires, while NHTSA advises consumers to select tires that meet the vehicle maker’s recommendations. Neither a table nor a calculator can identify the correct tire for a particular vehicle without those vehicle-specific checks.