How many shiplap boards do you need for a wall?

Finish Carpentry
Trim & Molding
Estimating & Takeoff

Shiplap is sold by nominal width and installed by coverage width, and the lap between them is the whole calculation. Count off the label and you finish a course short at the ceiling; measure the coverage and the order is right the first time. An M1 Caliber reads the actual covered face, and the app's fractional calculator divides the wall height into it in feet-inch-fraction without anybody converting to decimals. The count then comes off two measured numbers instead of a label and a guess.

How the board count is worked out

Coverage width, not nominal width
M1 reads the actual covered face
Fractional calculator does the divide
97.2 inch wall came to 20 pieces
M1 numbers feed the order directly

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The video works it out in the aisle: each piece measures 4 15/16 of coverage, the wall height is 97.2 inches, and dividing one into the other gives 20 pieces. The arithmetic is trivial. Getting the coverage width rather than the nominal width is the part that decides whether the order is correct.