Bike Size Chart: Frame Size by Height & Inseam 2026

How your bike size is worked out

On the defaults — 5 feet 9 inches (175.26 cm) tall, a 32-inch inseam (81.28 cm) — the road frame is 54.46 cm (about 54 cm), the mountain frame is 17.92 in (about 18 in), and the hybrid frame is 18.56 in (about 19 in). The whole calculation is three moves: convert the inseam to centimetres, multiply by the factor for each bike type, and convert back to inches where the frame is measured in inches. Height only picks the chart row — the inseam does the work.

Five things about the model are worth stating plainly. First, the road frame in centimetres is the inseam in centimetres times 0.67. Second, the mountain frame in inches is the inseam in centimetres times 0.56, divided by 2.54 — the centimetres-to-inches conversion. Third, the hybrid frame in inches is the inseam in centimetres times 0.58, divided by 2.54. Fourth, the inseam in centimetres is the inseam in inches times 2.54. And fifth, the chart row comes from height alone — and the calculator’s answer can sit just outside the row, as it does on the defaults, because two riders the same height can have different inseams.

Bike size chart: frame size by height and inseam

The chart is the standard starting point. Find your height, read across for your inseam, and the frame sizes follow. The calculator below refines it from your exact inseam.

The worked example, line by line

Setup: 5 feet 9 inches tall (69 in = 175.26 cm), inseam 32 in (81.28 cm).

Line 1 — convert the inseam to centimetres. The inseam is 32 × 2.54 = 81.28 cm.

Line 2 — multiply by the road factor. The road frame is 81.28 × 0.67 = 54.46 cm, about 54 cm.

Line 3 — multiply by the mountain and hybrid factors. The mountain frame is 81.28 × 0.56 ÷ 2.54 = 17.92 in, about 18 in; the hybrid frame is 81.28 × 0.58 ÷ 2.54 = 18.56 in, about 19 in.

Line 4 — check the chart row. At 5'9" the row is 5'8"–5'10", which says road 55–56 cm, mountain 18 in, hybrid 18–19 in. The calculator’s 54 cm sits just under the row — inseam, not height, is doing the work. Rounding convention: totals are computed from unrounded values, so rounded parts may differ by a hundredth from their rounded sum.

Every branch, checked

5'4", inseam 30 in: Height 5 feet 4 inches (162.56 cm), inseam 30.00 in (76.20 cm): road frame 51.05 cm (about 51 cm), mountain frame 16.80 in (about 17 in), hybrid frame 17.40 in (about 17 in), chart row 5'4"–5'6" — a shorter rider with a 30-inch inseam takes a 51 cm road frame.

6'0", inseam 34 in: Height 6 feet 0 inches (182.88 cm), inseam 34.00 in (86.36 cm): road frame 57.86 cm (about 58 cm), mountain frame 19.04 in (about 19 in), hybrid frame 19.72 in (about 20 in), chart row 6'0"–6'2" — a taller rider with a 34-inch inseam takes a 58 cm road frame.

5'0", inseam 28 in: Height 5 feet 0 inches (152.40 cm), inseam 28.00 in (71.12 cm): road frame 47.65 cm (about 48 cm), mountain frame 15.68 in (about 16 in), hybrid frame 16.24 in (about 16 in), chart row 5'0"–5'2" — a 28-inch inseam takes a 48 cm road frame.

6'4", inseam 36 in: Height 6 feet 4 inches (193.04 cm), inseam 36.00 in (91.44 cm): road frame 61.26 cm (about 61 cm), mountain frame 20.16 in (about 20 in), hybrid frame 20.88 in (about 21 in), chart row 6'4"–6'6" — a 36-inch inseam takes a 61 cm road frame.

Inseam 30 in at 5'9": Height 5 feet 9 inches (175.26 cm), inseam 30.00 in (76.20 cm): road frame 51.05 cm (about 51 cm), mountain frame 16.80 in (about 17 in), hybrid frame 17.40 in (about 17 in), chart row 5'8"–5'10" — the same inseam as the 5'4" rider, the same answer: inseam rules, not height.

Inseam 34 in at 5'9": Height 5 feet 9 inches (175.26 cm), inseam 34.00 in (86.36 cm): road frame 57.86 cm (about 58 cm), mountain frame 19.04 in (about 19 in), hybrid frame 19.72 in (about 20 in), chart row 5'8"–5'10" — the same inseam as the 6'0" rider, the same answer again.

5'6", inseam 31 in: Height 5 feet 6 inches (167.64 cm), inseam 31.00 in (78.74 cm): road frame 52.76 cm (about 53 cm), mountain frame 17.36 in (about 17 in), hybrid frame 17.98 in (about 18 in), chart row 5'6"–5'8" — a 31-inch inseam takes a 53 cm road frame.

The reverses, worked backwards

Inseam for a 56 cm road frame: 32.91 in — the exact inseam is 32.9063 in. At the displayed 32.91 in the road frame is 56.01 cm, 1 hundredth over the 56 cm target — rounding. 32.90 in gives 55.99 cm; 32.92 in gives 56.02 cm. The star is INCHES.

Inseam for a 19 in mountain frame: 33.93 in — the exact inseam is 33.9286 in. At the displayed 33.93 in the mountain frame is 19.00 in (exact to the hundredth). 33.92 in gives 19.00 in; 33.94 in gives 19.01 in. The star is INCHES.

Inseam at which the road frame first reaches 58 cm: 34.25 in — the smallest 0.25-inch step that clears 58 cm. At 34.25 in the road frame is 58.29 cm; at 34.00 in it is 57.86 cm. This is a step reverse: inseams come in quarter-inch steps here, so there is no exact in-between. The star is INCHES.

Inseam for a 20 in hybrid frame: 34.48 in — the exact inseam is 34.4828 in. At the displayed 34.48 in the hybrid frame is 20.00 in (exact to the hundredth). 34.47 in gives 19.99 in; 34.49 in gives 20.00 in. The star is INCHES.

Inseam for a 60 cm road frame: 35.26 in — the exact inseam is 35.2568 in. At the displayed 35.26 in the road frame is 60.01 cm, 1 hundredth over the 60 cm target — rounding. 35.25 in gives 59.99 cm; 35.27 in gives 60.02 cm. The star is INCHES.

First height band whose road range starts at 59 cm: 6'0"–6'2" — a table lookup, not a calculation. The band below it, 5'10"–6'0", starts at 57 cm.

What the defaults assume

The defaults are 5 feet 9 inches tall with a 32-inch inseam — road frame 54.46 cm, mountain frame 17.92 in, hybrid frame 18.56 in. With an inseam of 24 in, Height 5 feet 9 inches (175.26 cm), inseam 24.00 in (60.96 cm): road frame 40.84 cm (about 41 cm), mountain frame 13.44 in (about 13 in), hybrid frame 13.92 in (about 14 in), chart row 5'8"–5'10" — a small frame all round. With an inseam of 40 in, Height 5 feet 9 inches (175.26 cm), inseam 40.00 in (101.60 cm): road frame 68.07 cm (about 68 cm), mountain frame 22.40 in (about 22 in), hybrid frame 23.20 in (about 23 in), chart row 5'8"–5'10" — the largest adult frames in the chart. With an inseam of 27 in, Height 5 feet 9 inches (175.26 cm), inseam 27.00 in (68.58 cm): road frame 45.95 cm (about 46 cm), mountain frame 15.12 in (about 15 in), hybrid frame 15.66 in (about 16 in), chart row 5'8"–5'10". With an inseam of 38 in, Height 5 feet 9 inches (175.26 cm), inseam 38.00 in (96.52 cm): road frame 64.67 cm (about 65 cm), mountain frame 21.28 in (about 21 in), hybrid frame 22.04 in (about 22 in), chart row 5'8"–5'10". At a height of 4'0" you are below the chart — kids’ bikes (24-inch wheels or smaller), no adult frame size. With an inseam of 0 in, Height 5 feet 9 inches (175.26 cm), inseam 0.00 in (0.00 cm): road frame 0.00 cm (about 0 cm), mountain frame 0.00 in (about 0 in), hybrid frame 0.00 in (about 0 in), chart row 5'8"–5'10". Rounding convention: totals are computed from unrounded values, so rounded parts may differ by a hundredth from their rounded sum.

Output · formula · meaning

Who uses this

• The 5'9" rider with a 32-inch inseam: they learn the road frame is 54.46 cm — about 54 cm — and the mountain frame is 17.92 in — and they check the 32.91-inch reverse to see what inseam it takes to reach a 56 cm road frame.
• The 6'0" rider with a 34-inch inseam: they learn the road frame is 57.86 cm — about 58 cm — and the hybrid frame is 19.72 in — and they check the 34.25-inch step to see the first inseam that clears a 58 cm road frame.
• The between-sizes rider: they learn the chart row for 5'9" says 55–56 cm while the calculator says 54 cm — and they check the 6'0"–6'2" band to see where the 59 cm road frames start.
• The parent sizing a kids’ bike: they learn a 4'0" rider is below the chart — kids’ bikes, 24-inch wheels or smaller — and they check the 24-inch inseam edge to see the smallest adult frame, 41 cm.

Accuracy & limitations

The math is first-principles: the inseam in centimetres is the inseam in inches times 2.54; the road frame in centimetres is the inseam in centimetres times 0.67; the mountain frame in inches is the inseam in centimetres times 0.56, divided by 2.54; the hybrid frame in inches is the inseam in centimetres times 0.58, divided by 2.54. Every figure is rounded to hundredths half-up, and the totals are computed from unrounded values, so rounded parts may differ by a hundredth from their rounded sum. What the model cannot do is tell you what YOUR frame size is: frame sizing varies by brand and by frame geometry — sloping top tubes, reach, and stack all change the fit, so two frames with the same seat-tube length can ride very differently; it does NOT model your arm length, torso length, or flexibility, which decide the reach and the handlebar height; it does NOT model kids’ bikes below 4'6", which use wheel size rather than frame size; and it does NOT model the difference between a frame’s listed size and its effective size on a sloping top tube. Use it as the standard starting point, then take a test ride before you buy.

Frequently asked questions