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Sine bar calculator

A sine bar turns an angle into a length: H = L·sin θ. Setting 15° on a 100 mm sine bar takes a 25.882 mm gauge block stack. Enter the angle to get the stack — or the stack you actually built to get the angle it truly sets. Works for sine plates and either the 100/200 mm or 5/10 in centre distances.

Accuracy falls off as the angle grows (the sine flattens), which is why setups past ~45° usually measure the complement instead.

Stack gauge blocks to the computed height; the bar tilts to the target angle.

Bar-length presets own their units, so the height result uses the selected bar unit and ignores the global display-unit preference.

Stack height
2.5000in

Stack height = L·sin(θ). In reverse, θ = asin(stack height ÷ L).

Angle formats: unit converter.

Derived

Computed from the standard sine-bar formula h = L·sin(θ) and its inverse

Values follow the governing standard, which is authoritative for production and inspection decisions. Verify against it before you rely on a number.

Standard names are trademarks of their respective owners; ASdrawn is not affiliated with or endorsed by any standards body.

How does a sine bar set an angle?

A sine bar is a hardened bar with two precision rolls a fixed centre distance apart. Rest one roll on a surface plate and lift the other on a stack of gauge blocks, and the bar tilts to an angle whose sine is the stack height over the centre distance: H = L·sin θ. Build the stack, and the angle is set — no protractor required.

Enter the target angle and this calculator returns the exact stack height for a 100/200 mm or 5/10 in bar; enter a stack you actually built and it returns the angle it truly produces. Because sine flattens near 90°, a small block error swings the angle more as the setup steepens — which is why steep angles are usually set from the complement.