What is saddle setback?

It is the horizontal distance between the tip of your saddle and a vertical line through the centre of the bottom bracket. On most road bikes the saddle nose sits 40 to 80 mm behind the bottom bracket.

Is saddle setback the same as KOPS?

No. Setback measures where the saddle is. KOPS measures where your knee is over the pedal axle with the crank at 3 o'clock, which also depends on your femur length and how you sit. Two riders with the same setback can have very different KOPS numbers.

Does moving the saddle back change my saddle height?

Yes. Sliding the saddle back on the rails moves it further from the bottom bracket, so your effective saddle height goes up. Move the saddle back 10 mm and you usually need to drop it a few millimetres to keep the same leg extension.

Why does the calculator ask for the nose-to-clamp distance?

Because saddles differ. A 240 mm short-nose saddle and a 275 mm traditional saddle clamped at the same point put the nose in very different places. Measuring your own saddle keeps the result honest.

What effective seat angle should I use?

Start with the number on your frame's geometry chart. If your seatpost has offset, or you have slid the saddle a long way on the rails, your real effective angle is different. Measure your setback and use the reverse calculator above to find the angle it matches.

Saddle setback calculator

Enter your saddle height and effective seat-tube angle to see how far behind the bottom bracket your saddle sits, and how that compares with the range for your riding style.

Saddle height (cm)Bottom bracket centre to the top of the saddle, along the seat tube.Effective seat-tube angle (°)From your frame's geometry chart. Most road frames are 73 to 74.5°.Saddle nose to seatpost clamp (mm)Measured along the saddle, from the nose to where the post clamps the rails. About 130 mm on a 270 mm road saddle clamped mid-rail.Riding style

Saddle nose behind the bottom bracket

77.3 mm

Typical range for your style

58.9 mm to 89.5 mm

Calculated from your own saddle height, so it scales with your leg length instead of assuming an average rider.

Seatpost axis behind the bottom bracket: 207.3 mm

Already measured your setback?

Measured nose setback (mm)Use a negative number if the nose is ahead of the bottom bracket.

Enter a measured setback to see the seat angle it matches.

How to measure saddle setback on the bike

Stand the bike level against a wall. Hang a plumb line from the tip of the saddle and mark the floor. Do the same from the centre of the bottom bracket. The distance between the two marks is your setback. Measure the nose-to-clamp distance separately, along the top of the saddle.

Why this result?

The saddle top sits on the seatpost axis, and that axis leans back from the bottom bracket at the effective seat-tube angle. So the horizontal offset of the post at your saddle height is saddle height × cos(seat angle). The saddle nose sits forward of the post by the nose-to-clamp distance, which is subtracted.

The range shown is not a fixed table. It is the same formula run at the seat angles each riding style normally uses: 72.5 to 75° for road and endurance, 76 to 80° for time trial and triathlon. Because it starts from your saddle height, it moves with your leg length.

Where these numbers come from

The seat-angle bands come from published road and time-trial frame geometry, not from a fitting rule of thumb.
The setback itself is trigonometry on the seat-tube triangle, so it is exact for the numbers you enter.
KOPS measures something different: where your knee sits over the pedal axle, not where the saddle is.

Frequently asked questions

What is saddle setback?: It is the horizontal distance between the tip of your saddle and a vertical line through the centre of the bottom bracket. On most road bikes the saddle nose sits 40 to 80 mm behind the bottom bracket.
Is saddle setback the same as KOPS?: No. Setback measures where the saddle is. KOPS measures where your knee is over the pedal axle with the crank at 3 o'clock, which also depends on your femur length and how you sit. Two riders with the same setback can have very different KOPS numbers.
Does moving the saddle back change my saddle height?: Yes. Sliding the saddle back on the rails moves it further from the bottom bracket, so your effective saddle height goes up. Move the saddle back 10 mm and you usually need to drop it a few millimetres to keep the same leg extension.
Why does the calculator ask for the nose-to-clamp distance?: Because saddles differ. A 240 mm short-nose saddle and a 275 mm traditional saddle clamped at the same point put the nose in very different places. Measuring your own saddle keeps the result honest.
What effective seat angle should I use?: Start with the number on your frame's geometry chart. If your seatpost has offset, or you have slid the saddle a long way on the rails, your real effective angle is different. Measure your setback and use the reverse calculator above to find the angle it matches.

Related guides

KOPS explained — Knee Over Pedal Spindle: what the plumb-line test actually measures, what offset is normal for road and TT, and how to move your saddle fore-aft.
Road bike fit angles — The complete reference chart for a road position: knee, hip, torso, elbow and shoulder angles plus KOPS, with target ranges and what to change when a number is off.

Other tools

Saddle height calculator — Estimate your saddle height from inseam with the LeMond method, measured from the bottom bracket to the top of the saddle.
Stem length calculator — Compare two stem setups and see how much reach and height you gain or lose from stem length, stem angle and spacers.

Check this with a photo

Setback tells you where the saddle is. It does not tell you where your knee ends up. Pedalyze measures your real knee-over-pedal offset from a photo of you on the bike, at the crank position where it counts.

Check my bike fit