Frame map

The dots are frame sizes: if one lies in the green box, it fits your height and your position.

Race, endurance or gravel? At the same size the bar sits 2 to 3 cm higher on endurance and gravel bikes than on a race bike. The difference, with a picture

For you: Race 56 and 58. With more spacers, the 54 too.

181 cm, Bar 6.5 cm below the saddle · Example

Map: reach to the right, stack upwards; the boxes show where a frame fits, the dots are the frame sizes of your kind of bike. Race 44: stack 501, reach 366 · does not fit. Height: too low at the front, even with 4 cm of spacers. Length: a little short, only with a longer stem than usual. Saddle: fits, 269 mm of seatpost showing. Fits up to 162 cm body height, inseam up to 75 cm. 44 Race 49: stack 514, reach 375 · does not fit. Height: too low at the front, even with 4 cm of spacers. Length: fits with the stock stem for your height. Saddle: fits, 252 mm of seatpost showing. Fits up to 166 cm body height, inseam up to 77 cm. 49 Race 52: stack 527, reach 380 · does not fit. Height: too low at the front, even with 4 cm of spacers. Length: fits with the stock stem for your height. Saddle: fits, 229 mm of seatpost showing. Fits from 160 to 170 cm body height, inseam 74 to 79 cm. 52 Race 54: stack 544, reach 384 · fits with tweaks. Height: high enough only with more spacers, up to 4 cm. Length: fits with the stock stem for your height. Saddle: fits, 206 mm of seatpost showing. Fits from 165 to 175 cm body height, inseam 76 to 81 cm. 54 Race 56: stack 565, reach 395 · fits. Height: fits with 0 to 2 cm of spacers. Length: fits with the stock stem for your height. Saddle: fits, 180 mm of seatpost showing. Fits from 171 to 182 cm body height, inseam 79 to 84 cm. 56 Race 58: stack 591, reach 402 · fits. Height: fits with 0 to 2 cm of spacers. Length: fits with the stock stem for your height. Saddle: fits, 152 mm of seatpost showing. Fits from 178 to 189 cm body height, inseam 82 to 88 cm. 58 Race 61: stack 612, reach 408 · does not fit. Height: too high at the front, even without spacers. Length: fits with the stock stem for your height. Saddle: the seat tube is too long for your legs, only 123 mm of seatpost showing. Fits from 185 to 196 cm body height, inseam 86 to 91 cm. 61
Tap a dot or anywhere on the map.
  • fits
  • fits with tweaks
  • just about fits
  • does not fit
Finding your position

If you sit well on your bike, measure it: from the top of the saddle level forwards, then straight down to the top of the handlebar.

Race bikes come with about 7 cm, endurance bikes with about 5 cm, trekking bikes with the bar at saddle height.

If you can't reach your toes with straight legs, set it more upright. When in doubt, too: lower is easy later with fewer spacers, higher often isn't.

Stretched like on a race bike. Fast, takes flexibility in the hips and back.

On the bike that means: Bar 6.5 cm below the saddle

Race 58: stack 591, reach 402 · fits

Height: fits with 0 to 2 cm of spacers. Length: fits with the stock stem for your height. Saddle: fits, 152 mm of seatpost showing. Fits from 178 to 189 cm body height, inseam 82 to 88 cm.

Open in “Set up your bike”

How this is worked out

Fits: height and length are right with the stock stem and 0 to 2 cm of spacers above a flat top cap; moving spacers costs nothing. With tweaks: with more spacers, up to 4 cm. The right frame does not need a flipped stem. Just about: only with a stem shorter or longer than usual. Whether the saddle fits, each dot says for itself: that depends on the seat tube of a real frame. Bigger frames are mainly taller: about 2.7 centimetres of stack per centimetre of reach. Real frames mostly sit less than a centimetre off their line; a size means something different at every brand, which is why stack and reach count.

How to read the map

  1. Your body says where the bar should go: how far below the saddle and how far in front of it.
  2. Every frame in the green box puts it there, with the stem bikes of your size come with and 0 to 2 cm of spacers; in the lighter margin below it you need more spacers, in the yellow one beside it a different stem.
  3. The dots are frame sizes, small at the bottom left, big at the top right: where the row runs through the box, that size fits. Tap a dot to see whether the saddle fits too and from which to which body height the size fits; tap beside it to check a frame of your own.
  4. The position slider moves the box up or down: lower means sportier.
  5. Your bike is the ring with the arrow; stem and spacers move the arrow, so you see what a tweak does.

Without your measurements an example is shown: 181 cm, road bike, balanced, with average proportions. Enter your height above, and the map holds for you.

Which size fits how many?

A size chart names one frame size for every body height. But people of the same height have legs and arms of different lengths, and each gets their own window. Here you see, for how many people of a body height the calculator says “fits” for a frame size, in percent.

Race · Height (cm)
64 26 35 155 66 74 40 12 160 56 73 42 16 165 39 67 24 26 170 39 70 24 175 56 61 18 180 14 71 42 21 185 22 71 29 190 33 67 195 99 200 44 49 52 54 56 58 61 none

Race at 181 cm:

  • Size 56 fits 46% of people.
  • Size 58 fits 69% of people.
  • Size 61 fits 15% of people.
For 17% no size of this series fits directly, for 4% not even with a tweak or just barely.
  • fits directly
  • at least with a tweak or just barely
  • no size fits directly
  • what a size chart picks

Why it varies: legs and arms at 181 cm

Each square is a person of your height with different legs and arms. The number is the size that fits them best: bold where it fits directly, pale where it only works with a tweak or just barely. Empty: no size of the series works. The inner ring encloses two thirds of the people of your height, the outer one nine tenths.

Race · Inseam (cm) to the right, arm length (cm) upward
58 58 58 61 61 61 58 58 58 58 61 61 58 58 58 58 58 61 61 61 56 58 58 58 58 61 58 58 56 56 58 58 58 58 58 56 56 56 58 58 58 58 56 56 56 56 58 58 56 56 56 56 56 58 56 58 56 56 56 56 56 56 58 56 56 56 56 56 56 56 56 56 56 56 56 56 54 79 58 82 60 84 62 86 63 88 65 estimated
  • 44
  • 49
  • 52
  • 54
  • 56
  • 58
  • 61

This is a calculation with the spread of proportions (ANSUR II, around 6,000 people), not a count of real riders. A person can fit two sizes and then counts for both, so a column adds up to more than 100%.

What moves the window and what moves your bike

Your window (green) lies where your body and position put it. Your bike is a dot. Both can be moved, but in different directions: blue arrows move the window, black ones your bike. The scale is the same in both directions, so the angles are true.

your window 54 56 58 61 Arm ±1.7 cm Inseam ±2.2 cm Position: 3 cm more upright 3 cm sportier Spacers +10 mm Stem +10 mm one size up Race 58
  • The arm moves the window horizontally: about 7 mm of reach per centimetre, and no stack.
  • The inseam moves it diagonally: for every centimetre longer, about 7 mm less reach and 6 mm more stack.
  • Your position moves it almost vertically: from 3 cm sportier to 3 cm more upright the window lies 60 mm higher but only about 12 mm longer.
  • One frame size up takes the head tube about 21 mm higher but only about 6 mm forward.
  • A stem 10 mm longer gives about 10 mm of reach, two spacers (10 mm) about 10 mm of height.

So a size mainly changes the height. If you are short of length (longer arms, a shorter torso), the most economical way to get it is the stem, without taking the height along.

  • moves the window
  • moves your bike

Calculated for the position you set, with the proportions of the average person of your height. The window arrows show one standard deviation of the proportions (ANSUR II) in each direction.

How precise is the window?

At the same body height, people have legs and arms of different lengths. That moves the window that fits them. The bars show how far it can wander for two thirds of the people of your height: dark is the window, light its room to move. Every measurement you take makes the bar narrower.

Reach (mm)
340 360 380 400 420 440 460 Body height only · you ±15 mm + inseam · if you measure ±12 mm + inseam and arm length · if you measure ±7 mm

If the page knows only your body height, the reach window can wander by about ±15 mm, which is around 2 frame sizes. With everything measured it is still ±7 mm.

Stack (mm)
520 540 560 580 600 620 640 Body height only · you ±15 mm + inseam · if you measure ±3 mm + inseam and arm length · if you measure ±3 mm

The height depends on the inseam: ±15 mm without it, ±3 mm with it.

  • Window that fits
  • how far it can wander

The inseam is worth measuring next: it sharpens the window in height and length.

Measured does not mean exact: arm length with a tape measure alone to about ±1 cm, inseam to about ±0.5 cm. That is included. The spread of proportions comes from a survey of around 6,000 people (ANSUR II) and is a calculation, not a measurement of you.

Where the areas come from

It is the calculator’s verdict for every stack and every reach at once, the way you look for a frame: the same rule for every frame, race or endurance. It uses the angles usual at your saddle height and the stock stem, and only spacers raise or lower the bar. If you enter a bike you already own in the calculator, it may also count a flipped stem. That is why it sometimes says “fits with tweaks” where the map shows “does not fit”. If you have a model in mind, enter its stack and reach in the calculator; there you find the exact calculation for exactly that bike.

The window as numbers: frame size calculator