Practical workshop tools

Slab Yield and Kerf Calculator

Compare slab thickness, blade kerf and end allowance, then copy a geometric planning summary for your lapidary project.

By John Morris·Updated October 5, 2026·How we research

Geometric estimate

32possible slabs before defects and finishing losses

1.24 inseparating-cut loss

0.26 inremaining length

Carry this scenario into your project notes

Copy the measurements, geometric result and exclusions. The site does not save the scenario or create an account.

Slab Yield geometric planning summary
Inputs: 10 in slicing length; 0.25 in target slab thickness; 0.04 in kerf; 0.5 in total facing/trimming allowance.
Result: 32 possible slabs; 1.24 in separating-cut loss; 0.26 in remaining length.
All measurements are in inches. The arithmetic assumes one separating cut between adjacent slabs (n−1 cuts).
Not included: irregular surfaces, fractures, changing cross-section, workholding, orientation, end separation beyond the entered allowance, or later shaping and polishing losses.

Compare scenarios before choosing a cut plan

A scenario should answer one narrow question: how do thickness, kerf and total end allowance change straight-slice geometry? Keep the rock orientation and slicing direction consistent while comparing. If you change the orientation or planned face, measure the available length again.

Illustrative arithmetic

40 mm comparison

40 mm length, 6 mm slabs, 0.6 mm kerf and 4 mm total allowance produce 5 geometric slabs, 2.4 mm of separating-cut loss and 3.6 mm remaining.

Illustrative arithmetic

60 mm comparison

60 mm length, 5 mm slabs, 1 mm kerf and 6 mm total allowance produce 9 geometric slabs, 8 mm of separating-cut loss and 1 mm remaining.

These values demonstrate the arithmetic. They are not recommended slab thicknesses, blade specifications or claims about actual recovery.

Turn the estimate into a practical worksheet

Record the exact blade and its documented cut width; blade core thickness is not a substitute for measured or documented kerf.
Reserve one total allowance for facing, end preparation and any final separation you expect. Do not count the displayed remainder as automatically recoverable material.
Mark cracks, cavities and changing cross-section separately. Reduce the geometric slab count only after inspecting the actual specimen and orientation.
Confirm stock height, workholding, coolant and blade compatibility outside this calculator before cutting.

Know what the number means

The calculation uses the available length after your total allowance and assumes one separating cut between adjacent slabs. It rounds down to whole slabs. A final slab is treated as usable without an additional cut beyond the allowance entered.

Formula: floor((length − allowance + kerf) ÷ (thickness + kerf)). A result of zero means the available length cannot provide one slab at your chosen thickness.

This is not a cutting plan or a machine-capacity check. Irregular surfaces, fractures, workholding, orientation and later grinding can reduce yield. Use the estimate to compare material-loss scenarios, then assess the real specimen.

Understand blade kerf · Check stock-height guidance · Plan preform layout after slicing

Understand the assumptions

Projects

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