Tire Sizing
Before you can determine the replacement tire that best fits your lifestyle, you must first find the tire that properly fits your vehicle. Identifying the proper replacement tire size is more than merely measuring the radius. It considers factors such as aspect ratio, load index, speed rating, metric type and more.
By using our site, you can easily find what fits you. Click on the Find Your Tire navigation above and simply enter your vehicle information and follow our lead. We’ll show you the Ironman Tires that are right for your vehicle.*
If you prefer to do a little math to find your tire size, you can use the following calculations:
Example: Size 275/55R20
- 275 (mm) / 25.4 = 10.8 inches
- 10.8 x .55 = 5.94
- (5.94 x 2) + 20 = 31.88 inches
Section Width / 25.4 = SWi (converts mm to inches)
SWi x Aspect Ratio = Section Height (SH)
(SH x 2) + Rim Diameter Outside Diameter
Load Index Table
LI | kg | LBS | LI | kg | LBS | LI | kg | LBS | LI | kg | LBS |
---|---|---|---|---|---|---|---|---|---|---|---|
0 | 45 | 99.2 | 70 | 335 | 738.5 | 140 | 2500 | 5511.5 | 210 | 19000 | 41887.1 |
1 | 46.2 | 101.9 | 71 | 345 | 760.6 | 141 | 2575 | 5676.8 | 211 | 19500 | 42989.4 |
2 | 47.5 | 104.7 | 72 | 355 | 782.6 | 142 | 2650 | 5842.2 | 212 | 20000 | 44091.7 |
3 | 48.7 | 107.4 | 73 | 365 | 804.7 | 143 | 2725 | 6007.5 | 213 | 20600 | 45414.5 |
4 | 50 | 110.2 | 74 | 375 | 826.7 | 144 | 2800 | 6172.8 | 214 | 21200 | 46737.2 |
5 | 51.5 | 113.5 | 75 | 387 | 853.2 | 145 | 2900 | 6393.3 | 215 | 21800 | 48060.0 |
6 | 53 | 116.8 | 76 | 400 | 881.8 | 146 | 3000 | 6613.8 | 216 | 22400 | 49382.7 |
7 | 54.5 | 120.1 | 77 | 412 | 908.3 | 147 | 3075 | 6779.1 | 217 | 23000 | 50705.5 |
8 | 56 | 123.5 | 78 | 425 | 936.9 | 148 | 3150 | 6944.4 | 218 | 23600 | 52028.2 |
9 | 58 | 127.9 | 79 | 437 | 963.4 | 149 | 3250 | 7164.9 | 219 | 24300 | 53571.4 |
10 | 60 | 132.3 | 80 | 450 | 992.1 | 150 | 3350 | 7385.4 | 220 | 25000 | 55114.6 |
11 | 51.5 | 113.5 | 81 | 462 | 1018.5 | 151 | 3450 | 7605.8 | 221 | 25750 | 56768.1 |
12 | 63 | 138.9 | 82 | 475 | 1047.2 | 152 | 3550 | 7826.3 | 222 | 26500 | 58421.5 |
13 | 65 | 143.3 | 83 | 487 | 1073.6 | 153 | 3650 | 8046.7 | 223 | 27250 | 60075.0 |
14 | 67 | 147.7 | 84 | 500 | 1102.3 | 154 | 3750 | 8267.2 | 224 | 28000 | 61728.4 |
15 | 69 | 152.1 | 85 | 515 | 1135.4 | 155 | 3875 | 8542.8 | 225 | 29000 | 63933.0 |
16 | 71 | 156.5 | 86 | 530 | 1168.4 | 156 | 4000 | 8818.3 | 226 | 30000 | 66137.6 |
17 | 73 | 160.9 | 87 | 545 | 1201.5 | 157 | 4125 | 9093.9 | 227 | 30750 | 67791.0 |
18 | 75 | 165.3 | 88 | 560 | 1234.6 | 158 | 4250 | 9369.5 | 228 | 31500 | 69444.4 |
19 | 77.5 | 170.9 | 89 | 580 | 1278.7 | 159 | 4375 | 9645.1 | 229 | 32500 | 71649.0 |
20 | 80 | 176.4 | 90 | 600 | 1322.8 | 160 | 4500 | 9920.6 | 230 | 33500 | 73853.6 |
21 | 82.5 | 181.9 | 91 | 615 | 1355.8 | 161 | 4625 | 10196.2 | 231 | 34500 | 76058.2 |
22 | 85 | 187.4 | 92 | 630 | 1388.9 | 162 | 4750 | 10471.8 | 232 | 35500 | 78262.8 |
23 | 87.5 | 192.9 | 93 | 650 | 1433.0 | 163 | 4875 | 10747.4 | 233 | 36500 | 80467.4 |
24 | 90 | 198.4 | 94 | 670 | 1477.1 | 164 | 5000 | 11022.9 | 234 | 37500 | 82672.0 |
25 | 92.5 | 203.9 | 95 | 690 | 1521.2 | 165 | 5150 | 11353.6 | 235 | 38750 | 85427.7 |
26 | 95 | 209.4 | 96 | 710 | 1565.3 | 166 | 5300 | 11684.3 | 236 | 40000 | 88183.4 |
27 | 97.5 | 214.9 | 97 | 730 | 1609.3 | 167 | 5450 | 12015.0 | 237 | 41250 | 90939.2 |
28 | 100 | 220.5 | 98 | 750 | 1653.4 | 168 | 5600 | 12345.7 | 238 | 42500 | 93694.9 |
29 | 103 | 227.1 | 99 | 775 | 1708.6 | 169 | 5800 | 12786.6 | 239 | 43750 | 96450.6 |
30 | 106 | 233.7 | 100 | 800 | 1763.7 | 170 | 6000 | 13227.5 | 240 | 45000 | 99206.3 |
31 | 109 | 240.3 | 101 | 825 | 1818.8 | 171 | 6150 | 13558.2 | 241 | 46250 | 101962.1 |
32 | 112 | 246.9 | 102 | 850 | 1873.9 | 172 | 6300 | 13888.9 | 242 | 47500 | 104717.8 |
33 | 115 | 253.5 | 103 | 875 | 1929.0 | 173 | 6500 | 14329.8 | 243 | 48750 | 107473.5 |
34 | 118 | 260.1 | 104 | 900 | 1984.1 | 174 | 6700 | 14770.7 | 244 | 50000 | 110229.3 |
35 | 121 | 266.8 | 105 | 925 | 2039.2 | 175 | 6900 | 15211.6 | 245 | 51500 | 113536.2 |
36 | 125 | 275.6 | 106 | 950 | 2094.4 | 176 | 7100 | 15652.6 | 246 | 53000 | 116843.0 |
37 | 128 | 282.2 | 107 | 975 | 2149.5 | 177 | 7300 | 16093.5 | 247 | 54500 | 120149.9 |
38 | 132 | 291.0 | 108 | 1000 | 2204.6 | 178 | 7500 | 16534.4 | 248 | 56000 | 123456.8 |
39 | 136 | 299.8 | 109 | 1030 | 2270.7 | 179 | 7750 | 17085.5 | 249 | 58000 | 127866.0 |
40 | 140 | 308.6 | 110 | 1060 | 2336.9 | 180 | 8000 | 17636.7 | 250 | 60000 | 132275.1 |
41 | 145 | 319.7 | 111 | 1090 | 2403.0 | 181 | 8250 | 18187.8 | 251 | 61500 | 135582.0 |
42 | 150 | 330.7 | 112 | 1120 | 2469.1 | 182 | 8500 | 18739.0 | 252 | 63000 | 138888.9 |
43 | 155 | 341.7 | 113 | 1150 | 2535.3 | 183 | 8750 | 19290.1 | 253 | 65000 | 143298.1 |
44 | 160 | 352.7 | 114 | 1180 | 2601.4 | 184 | 9000 | 19841.3 | 254 | 67000 | 147707.2 |
45 | 165 | 363.8 | 115 | 1215 | 2678.6 | 185 | 9250 | 20392.4 | 255 | 69000 | 152116.4 |
160 | 170 | 374.8 | 116 | 1250 | 2755.7 | 186 | 9500 | 20943.6 | 256 | 71000 | 156525.6 |
47 | 175 | 385.8 | 117 | 1285 | 2832.9 | 187 | 9750 | 21494.7 | 257 | 73000 | 160934.7 |
48 | 180 | 396.8 | 118 | 1320 | 2910.1 | 188 | 10000 | 22045.9 | 258 | 75000 | 165343.9 |
49 | 185 | 407.8 | 119 | 1360 | 2998.2 | 189 | 10300 | 22707.2 | 259 | 77500 | 170855.4 |
50 | 190 | 418.9 | 120 | 1400 | 3086.4 | 190 | 10600 | 23368.6 | 260 | 80000 | 176366.8 |
51 | 195 | 429.9 | 121 | 1450 | 3196.6 | 191 | 10900 | 24030.0 | 261 | 82500 | 181878.3 |
52 | 200 | 440.9 | 122 | 1500 | 3306.9 | 192 | 11200 | 24691.4 | 262 | 85000 | 187389.8 |
53 | 206 | 454.1 | 123 | 1550 | 3417.1 | 193 | 11500 | 25352.7 | 263 | 87500 | 192901.2 |
54 | 212 | 467.4 | 124 | 1600 | 3527.3 | 194 | 11800 | 26014.1 | 264 | 90000 | 198412.7 |
55 | 218 | 480.6 | 125 | 1650 | 3637.6 | 195 | 12150 | 26785.7 | 265 | 92500 | 203924.2 |
56 | 224 | 493.8 | 126 | 1700 | 3747.8 | 196 | 12500 | 27557.3 | 266 | 95000 | 209435.6 |
57 | 230 | 507.1 | 127 | 1750 | 3858.0 | 197 | 12850 | 28328.9 | 267 | 97500 | 215947.1 |
58 | 236 | 520.3 | 128 | 1800 | 3968.3 | 198 | 13200 | 29100.5 | 268 | 10000 | 220458.6 |
59 | 243 | 535.7 | 129 | 1850 | 4078.5 | 199 | 13600 | 29982.4 | 269 | 103000 | 227072.3 |
60 | 250 | 551.1 | 130 | 1900 | 4188.7 | 200 | 14000 | 30864.2 | 270 | 106000 | 233686.1 |
61 | 257 | 566.6 | 131 | 1950 | 4298.9 | 201 | 14500 | 31966.5 | 271 | 109000 | 240299.8 |
62 | 265 | 584.2 | 132 | 2000 | 4409.2 | 202 | 15000 | 33068.8 | 272 | 112000 | 246913.6 |
63 | 272 | 599.6 | 133 | 2060 | 4541.4 | 203 | 15500 | 34171.1 | 273 | 115000 | 253527.3 |
64 | 280 | 617.3 | 134 | 2120 | 4673.7 | 204 | 16000 | 35273.4 | 274 | 118000 | 260141.1 |
65 | 290 | 639.3 | 135 | 2180 | 4806.0 | 205 | 16500 | 36375.7 | 275 | 121000 | 266754.9 |
66 | 300 | 661.4 | 136 | 2240 | 4938.3 | 206 | 17000 | 37478.0 | 276 | 125000 | 275573.2 |
67 | 307 | 676.8 | 137 | 2300 | 5070.5 | 207 | 17500 | 38580.2 | 277 | 128500 | 283289.2 |
68 | 315 | 694.4 | 138 | 2360 | 5202.8 | 208 | 18000 | 39682.5 | 278 | 132000 | 291005.3 |
69 | 325 | 716.5 | 139 | 2430 | 5357.1 | 209 | 18500 | 40784.8 | 279 | 136000 | 299823.6 |
Tire Speed Ratings Symbols
SPEED SYMBOL | MAXIMUM SPEED (km/h) | SPEED SYMBOL | MAXIMUM SPEED(km/h) |
---|---|---|---|
A1 | 5 | K | 110 |
A2 | 10 | L | 120 |
A3 | 15 | M | 130 |
A4 | 20 | N | 140 |
A5 | 25 | P | 150 |
A6 | 30 | Q | 160 |
A7 | 35 | R | 170 |
A8 | 40 | S | 180 |
B | 50 | T | 190 |
C | 60 | U | 200 |
D | 65 | H | 210 |
E | 70 | V | 240 |
F | 80 | W | 270 |
G | 90 | Y | 300 |
J | 100 | ZR | OVER 240 |
*Fitment Guide Terms of Use: This tire sizing tool, the website and all contents thereof and all services are provided on an "as is" basis without any warranty or condition, express, implied or statutory. We specifically disclaim any implied warranties of title, merchantability, fitness for a particular purpose and non-infringement. We do not warrant or guarantee that the contents of the website or the information provided by the tire sizing tools will be accurate, up-to-date or otherwise reliable.
In no event shall we be liable for lost profits or any special, incidental, indirect, consequential or reliance damages arising out of or in connection with this sizing tool or our services, under any legal theory, even if we have been advised of the possibility of such damages and notwithstanding the failure of essential purposes of any limited remedy.