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This widely used road bike sizing method makes it easy to determine the correct bicycle frame size and saddle height for road riding.
The information in this article will help you find your correct bike frame size. If you’re trying to measure a bicycle frame, see my article that tells how to measure a bicycle frame.
What You Will Need
- A tape measure.
- A hardback book about an inch thick.
- Tape, or a pencil or marker of some kind.
- An assistant.
How to Measure Your Inseam
- To measure your inseam, stand straight with your back against a wall in your stocking feet. Be sure to keep your feet flat on the floor so you can get an accurate measurement.
- Take the book and put it between your legs with the spine of the book firmly in your crotch and the edge of the book straight against the wall.
- Have your assistant place a piece of tape or make a mark with a pencil or marker on the wall straight with the top edge of the book.
- Take the tape measure and measure from the floor to the edge of the tape or to the line you made on the wall.
- Repeat these steps a couple more times. If you get slightly different measurements each time, then use the average of the three measurements. This is your inseam measurement.
Road Bike Sizing – Calculation
- Frame Size: Take your inseam measurement and multiply by 0.65 to determine your frame size. For example, if your inseam is 30 inches, your frame size would be 19.5 inches (30″ x 0.65 = 19.5″).
- Saddle Height: Take your inseam measurement and multiply by 0.883 to determine your saddle height. For example, if your inseam is 30 inches, your saddle height would be 26.49 inches (30″ x 0.883 = 26.49″). This will be your approximate saddle height. There are many variables that affect this measurement such as the thickness of your shoes and cleats, padded cycling shorts, etc. This saddle height calculation will be a good starting point.
I’ve included the chart below to make the calculations easier.
| Inseam Length | Frame Size | Saddle Height | |||
|---|---|---|---|---|---|
| inches | cm | inches | cm | inches | cm |
| 26 | 66.0 | 16.9 | 42.9 | 23.0 | 58.3 |
| 26.5 | 67.3 | 17.2 | 43.8 | 23.4 | 59.4 |
| 27 | 68.6 | 17.6 | 44.6 | 23.8 | 60.6 |
| 27.5 | 69.9 | 17.9 | 45.4 | 24.3 | 61.7 |
| 28 | 71.1 | 18.2 | 46.2 | 24.7 | 62.8 |
| 28.5 | 72.4 | 18.5 | 47.1 | 25.2 | 63.9 |
| 29 | 73.7 | 18.9 | 47.9 | 25.6 | 65.0 |
| 29.5 | 74.9 | 19.2 | 48.7 | 26.0 | 66.2 |
| 30 | 76.2 | 19.5 | 49.5 | 26.5 | 67.3 |
| 30.5 | 77.5 | 19.8 | 50.4 | 26.9 | 68.4 |
| 31 | 78.7 | 20.2 | 51.2 | 27.4 | 69.5 |
| 31.5 | 80.0 | 20.5 | 52.0 | 27.8 | 70.6 |
| 32 | 81.3 | 20.8 | 52.8 | 28.3 | 71.8 |
| 32.5 | 82.6 | 21.1 | 53.7 | 28.7 | 72.9 |
| 33 | 83.8 | 21.5 | 54.5 | 29.1 | 74.0 |
| 33.5 | 85.1 | 21.8 | 55.3 | 29.6 | 75.1 |
| 34 | 86.4 | 22.1 | 56.1 | 30.0 | 76.3 |
| 34.5 | 87.6 | 22.4 | 57.0 | 30.5 | 77.4 |
| 35 | 88.9 | 22.8 | 57.8 | 30.9 | 78.5 |
| 35.5 | 90.2 | 23.1 | 58.6 | 31.3 | 79.6 |
| 36 | 91.4 | 23.4 | 59.4 | 31.8 | 80.7 |
| 36.5 | 92.7 | 23.7 | 60.3 | 32.2 | 81.9 |
| 37 | 94.0 | 24.1 | 61.1 | 32.7 | 83.0 |
| 37.5 | 95.3 | 24.4 | 61.9 | 33.1 | 84.1 |
| 38 | 96.5 | 24.7 | 62.7 | 33.6 | 85.2 |
| 38.5 | 97.8 | 25.0 | 63.6 | 34.0 | 86.3 |
| 39 | 99.1 | 25.4 | 64.4 | 34.4 | 87.5 |
| 39.5 | 100.3 | 25.7 | 65.2 | 34.9 | 88.6 |
| 40 | 101.6 | 26.0 | 66.0 | 35.3 | 89.7 |
| 40.5 | 102.9 | 26.3 | 66.9 | 35.8 | 90.8 |
| 41 | 104.1 | 26.7 | 67.7 | 36.2 | 92.0 |
| 41.5 | 105.4 | 27.0 | 68.5 | 36.6 | 93.1 |
| 42 | 106.7 | 27.3 | 69.3 | 37.1 | 94.2 |
| 42.5 | 108.0 | 27.6 | 70.2 | 37.5 | 95.3 |
| 43 | 109.2 | 28.0 | 71.0 | 38.0 | 96.4 |
| 43.5 | 110.5 | 28.3 | 71.8 | 38.4 | 97.6 |
| 44 | 111.8 | 28.6 | 72.6 | 38.9 | 98.7 |
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