What is effective seat tube angle?

Effective STA is the angle between a line from the BB to the saddle top and the horizontal. It differs from the actual seat tube angle when the saddle is moved forward or backward on its rails.

What is a typical seat tube angle?

Road bikes: 72-74 degrees. TT bikes: 75-80 degrees. Mountain bikes: 73-76 degrees. Steeper angles put you further forward over the pedals.

Why does seat tube angle matter?

It affects your position over the pedals, power delivery, and muscle recruitment. Steeper angles engage quadriceps more, while slacker angles use more glutes and hamstrings.

BikeCalcs

Seat Tube Angle Calculator — Effective STA

Calculate the effective seat tube angle from saddle position.

Saddle Height

From BB centre to saddle top

Saddle Setback

Horizontal distance behind BB

How We Calculate This

Effective Seat Tube Angle

Effective STA = 90 - atan(Saddle Setback / Saddle Height)

Setback is the horizontal distance the saddle is behind the bottom bracket centre. A greater setback means a slacker effective angle.

Frequently Asked Questions

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Last updated: 2025-02-20

All calculations are estimates. Always verify results and consult a professional bike fitter where appropriate.