What does my tire size mean, and how does another size compare?
Type the size the way your sidewall shows it. Free, no sign-up, nothing leaves your browser.
Copy the size from the sidewall, starting with any letters in front: P215/65R16 98H. Add the load index and speed rating after it if you have them. Spaces and capitals don't matter.
Fix one part of the size without retyping it. The plus and minus buttons step through the values this calculator supports, so you can watch the comparison move.
Optional. Type a second size to see how much taller, wider and longer around it is, what your speedometer would show, and how its ratings compare.
Fix one part of the size without retyping it. The plus and minus buttons step through the values this calculator supports, so you can watch the comparison move.
The Tire and Loading Information label on the driver's door pillar or door edge, after "Original tire size" or "Size". Add the load index and speed rating only if the label prints them.
Fix one part of the size without retyping it. The plus and minus buttons step through the values this calculator supports, so you can watch the comparison move.
The last four digits after DOT on the sidewall: week, then year. 2423 is week 24 of 2023. If the code isn't there, check the other side of the tire.
The last four digits after DOT on the sidewall: week, then year. 2423 is week 24 of 2023. If the code isn't there, check the other side of the tire.
Your tire size, read back
Example sizes. Type yours over them.
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Type the size from your sidewall to see it in plain words.
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Questions for your installer
Need someone to check these? Browse tire stores and tire service shops near you.
Inflate to the pressure on your door placard. The pressure molded on the sidewall is the tire's maximum, not the one to use.
Nominal sizes, worked out from the markings alone. A shop that can see your car and the tire can tell you what this page can't.
Nothing you type leaves your browser or is saved. Print and Copy are the only ways to keep it.
Tire size chart: what each part means
Every sidewall writes the size in the same order, left to right. Here's P215/65R16 98H, taken apart.
P215/65R1698H
| In P215/65R16 98H | What it means |
|---|---|
| P | P-metric passenger tire. No letter: metric passenger. LT: light truck. |
| 215 | Section width in millimeters, sidewall to sidewall. |
| 65 | Aspect ratio: sidewall height as a percentage of the width. |
| R | Radial construction. ZR: radial built for more than 149 mph. |
| 16 | Wheel diameter in inches. |
| 98 | Load index. Look it up in the load index chart. |
| H | Speed rating. Look it up in the speed rating chart. |
Light truck sizes read the same way: LT245/75R16 120/116S carries two load indexes, for single and dual mounting.
Flotation sizes are in inches: 31x10.50R15 is about 31 inches tall and 10.50 inches wide, for a 15-inch wheel.
Tire speed rating chart
The letter after the load index is the speed rating. These are the top speeds each one is rated for.
| Speed rating | Top speed | km/h | Yours |
|---|---|---|---|
| L | 75 mph | 120 | |
| M | 81 mph | 130 | |
| N | 87 mph | 140 | |
| P | 93 mph | 150 | |
| Q | 99 mph | 160 | |
| R | 106 mph | 170 | |
| S | 112 mph | 180 | |
| T | 118 mph | 190 | |
| U | 124 mph | 200 | |
| H | 130 mph | 210 | |
| V | 149 mph | 240 | |
| W | 168 mph | 270 | |
| Y | 186 mph | 300 | |
| (Y) | above 186 mph | above 300 |
H comes between U and V. The letters run in speed order, not alphabetical order.
ZR in the size means more than 149 mph (240 km/h). A rating in brackets, like (97Y), means more than 186 mph; the tire maker has the figure.
Source: U.S. Tire Manufacturers Association, Tire Care and Safety guide (speed symbols table) and Tire Information Service Bulletin Vol. 58 No. 1 (L); km/h as in UN Regulation No. 30. Last checked October 8, 2026.
Tire load index chart
The number before the speed rating is the load index. This is what one tire is rated to carry.
| Load index | Pounds per tire | kg | Yours |
|---|---|---|---|
| 60 | 551 | 250 | |
| 61 | 567 | 257 | |
| 62 | 584 | 265 | |
| 63 | 600 | 272 | |
| 64 | 617 | 280 | |
| 65 | 639 | 290 | |
| 66 | 661 | 300 | |
| 67 | 677 | 307 | |
| 68 | 694 | 315 | |
| 69 | 717 | 325 | |
| 70 | 739 | 335 | |
| 71 | 761 | 345 | |
| 72 | 783 | 355 | |
| 73 | 805 | 365 | |
| 74 | 827 | 375 | |
| 75 | 853 | 387 | |
| 76 | 882 | 400 | |
| 77 | 908 | 412 | |
| 78 | 937 | 425 | |
| 79 | 963 | 437 | |
| 80 | 992 | 450 | |
| 81 | 1,019 | 462 | |
| 82 | 1,047 | 475 | |
| 83 | 1,074 | 487 |
| Load index | Pounds per tire | kg | Yours |
|---|---|---|---|
| 84 | 1,102 | 500 | |
| 85 | 1,135 | 515 | |
| 86 | 1,168 | 530 | |
| 87 | 1,202 | 545 | |
| 88 | 1,235 | 560 | |
| 89 | 1,279 | 580 | |
| 90 | 1,323 | 600 | |
| 91 | 1,356 | 615 | |
| 92 | 1,389 | 630 | |
| 93 | 1,433 | 650 | |
| 94 | 1,477 | 670 | |
| 95 | 1,521 | 690 | |
| 96 | 1,565 | 710 | |
| 97 | 1,609 | 730 | |
| 98 | 1,653 | 750 | |
| 99 | 1,709 | 775 | |
| 100 | 1,764 | 800 | |
| 101 | 1,819 | 825 | |
| 102 | 1,874 | 850 | |
| 103 | 1,929 | 875 | |
| 104 | 1,984 | 900 | |
| 105 | 2,039 | 925 | |
| 106 | 2,094 | 950 | |
| 107 | 2,150 | 975 |
| Load index | Pounds per tire | kg | Yours |
|---|---|---|---|
| 108 | 2,205 | 1,000 | |
| 109 | 2,271 | 1,030 | |
| 110 | 2,337 | 1,060 | |
| 111 | 2,403 | 1,090 | |
| 112 | 2,469 | 1,120 | |
| 113 | 2,535 | 1,150 | |
| 114 | 2,601 | 1,180 | |
| 115 | 2,679 | 1,215 | |
| 116 | 2,756 | 1,250 | |
| 117 | 2,833 | 1,285 | |
| 118 | 2,910 | 1,320 | |
| 119 | 2,998 | 1,360 | |
| 120 | 3,086 | 1,400 | |
| 121 | 3,197 | 1,450 | |
| 122 | 3,307 | 1,500 | |
| 123 | 3,417 | 1,550 | |
| 124 | 3,527 | 1,600 | |
| 125 | 3,638 | 1,650 | |
| 126 | 3,748 | 1,700 | |
| 127 | 3,858 | 1,750 | |
| 128 | 3,968 | 1,800 | |
| 129 | 4,079 | 1,850 | |
| 130 | 4,189 | 1,900 |
That's the tire's rated load, not what it carries at every pressure. Use your door placard pressure and ask your installer about load capacity at that pressure.
The cited 2008 UN Regulation No. 30 lowers the allowed load for V, W and Y tires on cars built to go faster than 130, 149 and 168 mph.
Source: UN Regulations No. 30 (indexes to 120) and No. 54 (121 to 130), Annex IV, as published in the EU Official Journal in 2008. Pounds: our conversion, rounded to the nearest pound. Last checked October 8, 2026.
How the tire size calculator works
It reads the size you typed.
We split it the way a tire shop does: the letters in front, the width in millimeters, the aspect ratio, R for radial, the wheel size in inches, then the load index and speed rating. LT and flotation sizes like 31x10.50R15 work too. If a part doesn't add up, we tell you which one and stop. We don't guess.
It works out the height.
The sidewall is the width times the aspect ratio: on a 215/65R16 that's 215 x 0.65 = 139.75 mm. The whole tire is the wheel plus two sidewalls, 16 x 25.4 + 2 x 139.75 = 685.9 mm, or 27.00 inches. That's the same formula UN Regulation No. 30 uses for a tire's design diameter.
It compares like with like.
Differences come from the unrounded millimeters, then get rounded once. Put a 225/60R17 against that 215/65R16 and the new tire is 15.9 mm taller, 2.3% larger overall. When a difference is too small to show, you'll see less than 0.1%, never a zero.
It works out your speedometer.
A speedometer reads speed from how fast the wheels turn. A taller tire covers more road per turn, so the speedometer reads low: at an indicated 65 mph on that 225/60R17 you'd be doing about 66.5. We assume the gauge reads true on the size you compare against, and we name that size every time. Give us your placard size and that's the one we use.
It looks up the codes.
Load index and speed rating come from our two dated charts. A code they don't cover shows up as you typed it, with a question for your installer. We never swap it for the nearest value.
It stops short of a verdict.
Nominal isn't measured. The cited 2008 UN rule for approving car tires lets a new radial tire's diameter come out from 3% under to 4% over its nominal sidewall height on each side, which for a 215/65R16 is roughly 26.7 to 27.4 inches. Makers publish measured dimensions for each model, and those beat any calculator. So you get numbers and questions here, and no green tick.
Who this is for
You've got two tire sizes and one car. Maybe the shop is out of yours and offers the next one over, or a used set on bigger wheels turned up at the right price. Maybe you just want to know what 98H on your sidewall promises. Pickup owners weighing an LT size against a 31-inch flotation tire can put both in. We do the arithmetic and hand you the questions. The person mounting the tires answers them.
Car owner questions about tire sizes
What does the middle number on a tire size mean?
It's the aspect ratio: how tall the sidewall is, as a percentage of the tire's width. On a 215/65R16 the sidewall is 65% of 215 mm, which is 139.75 mm, about 5.5 inches. A lower number means a shorter sidewall for the same width. That's the nominal figure. A particular tire can measure a little differently.
Does tire size affect the speedometer?
Yes. A speedometer reads speed from how fast the wheels turn, so a taller tire makes it read low and a shorter one makes it read high. A tire 2.3% larger in diameter means about 66.5 mph at an indicated 65, and the odometer is off by the same share. Type both sizes into the calculator to see yours.
Is H or V the higher speed rating?
V, by a wide margin: 149 mph against H's 130 mph (240 and 210 km/h). The letters don't run in alphabetical order. H sits between U, at 124 mph, and V. Our speed rating chart lists every letter in speed order, with its source.
Can I use a lower speed rating on my tires?
Your vehicle maker sets the speed rating your car needs, and your placard or owner's manual says what it is. The tire makers' own guide is plain about going lower: the vehicle's speed then has to be held to the replacement tire's rating, and handling could be affected. Settle that with your installer before the tires go on.
Can I use a tire with a lower load index?
The tire makers' guide says never to choose a replacement with less load-carrying capacity than the original size at your placard pressure. It also warns that the load index alone doesn't settle the question. Put your placard size into the calculator and a lower index shows up as a question for your installer, who can check the rest.
What does XL mean on a tire?
XL means Extra Load, also marked REINFORCED: a tire whose carcass is built stronger than the standard tire of the same size. Its load index tells you how much it's rated to carry. If you're switching to or from XL, ask your installer what pressure the XL tire should run on your car.
What does ZR mean in a tire size?
ZR means the tire is built for more than 149 mph (240 km/h). The speed rating after the size gives the figure: W is 168 mph, Y is 186 mph. A service description in brackets, like (97Y), means more than 186 mph, and only the tire maker has the exact number. ZR with no speed rating at all? Ask the maker.
What does the P mean in a tire size?
P marks a P-metric tire, the passenger-car sizing system. A size with no letter in front, like 215/65R16, is the metric system, often called Euro-metric. The numbers mean the same thing, so the nominal size works out the same. They're still separate systems, and the tire makers' guide says to check your placard for which type your vehicle calls for.
How do I read the date code on a tire?
Find DOT on the sidewall and read the last four digits of the code after it. The first two are the week and the last two the year: 2423 means week 24 of 2023, the week that began Sunday, June 11. Federal rules make week 01 the first full Sunday-to-Saturday week of the year. Can't find it? On tires made since September 2009, check the side meant to face out. If the tire has no designated outside, the full code can be on either side.
What does 31x10.50R15 mean?
It's a flotation size, written in inches: about 31 inches tall and 10.50 inches wide, a radial, for a 15-inch wheel. That height is 787.4 mm, straight off the size. The calculator reads flotation and LT sizes side by side, so you can set one against something like LT265/75R16, which works out to 31.65 inches.
What does M+S mean on a tire?
Mud and snow. The tire makers' guide says the letters mark a tire meant for limited mud and snow service, and you'll see them on many all-season tires as well as winter ones. Tires that pass a snow traction test can also carry a mountain-and-snowflake symbol. The calculator reads M+S back to you and leaves every number alone.
Does anything I type get saved or sent?
No. Your browser does all the math. Nothing you type is sent anywhere or saved, and there's no account. Print and Copy summary are the only ways to keep a result, and both stay with you.
Tire size comparison: what a different size changes
Most swaps people weigh keep the overall diameter close and trade sidewall for wheel. Going from 215/65R16 to 225/60R17 adds an inch of wheel, gives back a little sidewall, and leaves the whole tire 0.63 inches taller. That diameter is what your speedometer and odometer feel. The width is what your wheel and fenders feel, and the sidewall is the part that's left between the rim and the road.
The ratings travel separately. A new size carries its own load index and speed rating, and the figures your car needs come from the vehicle maker: the placard on the driver's door pillar and the owner's manual. The tire makers' guide adds one more caution for all-wheel and four-wheel drive, where even small differences in outside diameter can damage the drivetrain. That's why the calculator lists questions, not answers. The shop can see the car; we can't.
Sources and last checked
Speed ratings come from the U.S. Tire Manufacturers Association's Tire Care and Safety guide (its speed symbols table, in mph and km/h) and, for L, its Tire Information Service Bulletin Vol. 58 No. 1. The km/h figures match UN Regulation No. 30. Load indexes 60 to 120 come from UN Regulation No. 30 and 121 to 130 from UN Regulation No. 54, as published in the EU's Official Journal in 2008; pounds are our conversion, rounded to the nearest pound the way federal rules round the load molded on passenger tires. Date codes follow 49 CFR 574.5, the placard FMVSS 110 and sidewall markings FMVSS 139.
These are the industry's standard code tables, taken from the 2008 regulation texts and the association's own guide and bulletin. The Tire and Rim Association's Year Book is a paid publication, and we didn't use it.
Chart data version 2026-10-07. Last checked October 8, 2026.
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