Cam Timing Calculator

Calculate duration, overlap and event-midpoint centerlines from measured valve opening and closing events. All angles are crankshaft degrees unless marked otherwise.

All Calculators

Intake opens: ° BTDC (ATDC = negative)

Intake closes: ° ABDC (BBDC = negative)

Exhaust opens: ° BBDC (ABDC = negative)

Exhaust closes: ° ATDC (BTDC = negative)

Checking lift used for all four events

Checking lift units

Results update as you type.

Results

Use the same checking lift, lash convention and measurement method for all events. Centerlines are midpoints of opening/closing events, not a direct measurement of peak lift; asymmetric lobes can produce different true lobe centerlines. The estimated separation is calculated from those event midpoints. Negative overlap means a closed-valve gap at this checking lift. This does not establish piston-to-valve clearance or recommend cam settings.

Formula and assumptions

Intake duration = 180 + IO + IC. Exhaust duration = 180 + EO + EC. Overlap = IO + EC. Intake midpoint ATDC = (180 + IC − IO) ÷ 2. Exhaust midpoint BTDC = (180 + EO − EC) ÷ 2. Estimated lobe separation (cam degrees) = (intake midpoint + exhaust midpoint) ÷ 2.