Part of the data ring
TireFit
Rim schedule180 sizes · 121 conventional

Tyre sizes for a
21-inch rim

180 sizes A 21-inch wheel takes 180 metric tyre sizes inside the physical envelope of a road tyre, from 135/45R21 at 655 mm to 325/50R21 at 858 mm.

121 of them sit inside the conventional fitment envelope and are listed first. The rest are arithmetically valid combinations that the market does not build, and they are marked as such rather than hidden.

Every size, shortest to tallest

Overall diameter under each. Sizes outside the conventional envelope are greyed.

135/45R21655 mm · uncommon 175/35R21656 mm · uncommon 245/25R21656 mm 205/30R21656 mm 155/40R21657 mm · uncommon 255/25R21661 mm 215/30R21662 mm 185/35R21663 mm · uncommon 145/45R21664 mm · uncommon 165/40R21665 mm · uncommon 265/25R21666 mm 135/50R21668 mm · uncommon 225/30R21668 mm 195/35R21670 mm 275/25R21671 mm 155/45R21673 mm · uncommon 175/40R21673 mm · uncommon 235/30R21674 mm 285/25R21676 mm 205/35R21677 mm 145/50R21678 mm · uncommon 245/30R21680 mm 295/25R21681 mm 185/40R21681 mm 135/55R21682 mm · uncommon 165/45R21682 mm · uncommon 215/35R21684 mm 305/25R21686 mm 255/30R21686 mm 155/50R21688 mm · uncommon 195/40R21689 mm 175/45R21691 mm 225/35R21691 mm 315/25R21691 mm 265/30R21692 mm 145/55R21693 mm · uncommon 135/60R21695 mm · uncommon 325/25R21696 mm 205/40R21697 mm 235/35R21698 mm 165/50R21698 mm · uncommon 275/30R21698 mm 185/45R21700 mm 335/25R21701 mm 155/55R21704 mm · uncommon 285/30R21704 mm 245/35R21705 mm 215/40R21705 mm 345/25R21706 mm 145/60R21707 mm · uncommon 175/50R21708 mm 135/65R21709 mm · uncommon 195/45R21709 mm 295/30R21710 mm 355/25R21711 mm 255/35R21712 mm 225/40R21713 mm 165/55R21715 mm · uncommon 305/30R21716 mm 205/45R21718 mm 185/50R21718 mm 265/35R21719 mm 155/60R21719 mm · uncommon 235/40R21721 mm 145/65R21722 mm · uncommon 135/70R21722 mm · uncommon 315/30R21722 mm 175/55R21726 mm 275/35R21726 mm 215/45R21727 mm 195/50R21728 mm 325/30R21728 mm 245/40R21729 mm 165/60R21731 mm · uncommon 285/35R21733 mm 335/30R21734 mm 155/65R21735 mm · uncommon 135/75R21736 mm · uncommon 225/45R21736 mm 145/70R21736 mm · uncommon 185/55R21737 mm 255/40R21737 mm 205/50R21738 mm 295/35R21740 mm 345/30R21740 mm 175/60R21743 mm 235/45R21745 mm 265/40R21745 mm 355/30R21746 mm 305/35R21747 mm 165/65R21748 mm · uncommon 195/55R21748 mm 215/50R21748 mm 135/80R21749 mm · uncommon 155/70R21750 mm · uncommon 145/75R21751 mm · uncommon 275/40R21753 mm 245/45R21754 mm 315/35R21754 mm 185/60R21755 mm 225/50R21758 mm 205/55R21759 mm 175/65R21761 mm · uncommon 325/35R21761 mm 285/40R21761 mm 255/45R21763 mm 165/70R21764 mm · uncommon 145/80R21765 mm · uncommon 155/75R21766 mm · uncommon 195/60R21767 mm 335/35R21768 mm 235/50R21768 mm 295/40R21769 mm 215/55R21770 mm 265/45R21772 mm 185/65R21774 mm · uncommon 345/35R21775 mm 305/40R21777 mm 175/70R21778 mm · uncommon 245/50R21778 mm 205/60R21779 mm 165/75R21781 mm · uncommon 225/55R21781 mm 275/45R21781 mm 155/80R21781 mm · uncommon 355/35R21782 mm 315/40R21785 mm 195/65R21787 mm · uncommon 255/50R21788 mm 285/45R21790 mm 215/60R21791 mm 235/55R21792 mm 185/70R21792 mm · uncommon 325/40R21793 mm 175/75R21796 mm · uncommon 165/80R21797 mm · uncommon 265/50R21798 mm 295/45R21799 mm 205/65R21800 mm · uncommon 335/40R21801 mm 245/55R21803 mm 225/60R21803 mm 195/70R21806 mm · uncommon 305/45R21808 mm 275/50R21808 mm 345/40R21809 mm 185/75R21811 mm · uncommon 215/65R21813 mm · uncommon 175/80R21813 mm · uncommon 255/55R21814 mm 235/60R21815 mm 315/45R21817 mm 355/40R21817 mm 285/50R21818 mm 205/70R21820 mm · uncommon 265/55R21825 mm 195/75R21826 mm · uncommon 225/65R21826 mm · uncommon 325/45R21826 mm 245/60R21827 mm 295/50R21828 mm 185/80R21829 mm · uncommon 215/70R21834 mm · uncommon 335/45R21835 mm 275/55R21836 mm 305/50R21838 mm 235/65R21839 mm · uncommon 255/60R21839 mm 205/75R21841 mm · uncommon 345/45R21844 mm 195/80R21845 mm · uncommon 285/55R21847 mm 225/70R21848 mm · uncommon 315/50R21848 mm 265/60R21851 mm 245/65R21852 mm · uncommon 355/45R21853 mm 215/75R21856 mm · uncommon 295/55R21858 mm 325/50R21858 mm

SOURCE·Metric size geometry + UN ECE R39 speedometer tolerance·180 designations, each computed from the size itself·REVIEWED ETRTO STANDARD

How the figures are derived

  1. Read the size as the specification it is: section width in millimetres, aspect ratio as a percentage of that width, rim diameter in inches.
  2. Sidewall height = width × aspect ÷ 100. This is the number the size string is really about, and it is the one nobody quotes.
  3. Overall diameter = rim × 25.4 + two sidewalls — one at the top of the wheel and one at the bottom.
  4. Circumference = π × overall diameter, which gives revolutions per kilometre and per mile directly.
  5. Nothing above is measured, estimated, averaged or dated. It is the definition of the designation, so it does not go stale and it has no source to cite beyond the standard itself.
sidewall (mm) = width × aspect ÷ 100
overall diameter (mm) = rim × 25.4 + 2 × sidewall
speedo true speed = indicated × (new diameter ÷ old diameter)

The full method, the ±3% rule, and what geometry cannot tell you →

About 21-inch fitments

How many tyre sizes are there for a 21-inch rim?

180 metric sizes fall inside the physical envelope of a road tyre on a 21-inch wheel, of which 121 sit inside the conventional fitment envelope. They range from 135/45R21 at 655 mm overall to 325/50R21 at 858 mm.

Does a bigger rim mean a bigger tyre?

Not usually. Going up a rim size while keeping the same overall diameter is the entire point of plus-sizing: the wheel grows, the sidewall shrinks by the same amount, and the rolling diameter — which is what the speedometer counts — stays put.

13″ 15314″ 17815″ 20216″ 22417″ 22818″ 21819″ 20620″ 19322″ 163
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Published by

Amit Sharma

Auckland real-estate agent and marketer. Builds free, sourced data tools.

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