Here’s how to plan your biscuit placement for a strong and even joint:

1. Measure Your Board: Enter the total length of the board or edge you are joining in inches.
2. Set End Spacing: Decide how far from each end you want the center of your first and last biscuit to be. A common distance is 3 to 4 inches.
3. Calculate Available Space: The calculator subtracts the two end spaces from the total board length to find the available length for the remaining biscuits.
4. Determine Biscuit Count & Spacing: Based on a general rule of thumb (spacing biscuits every 6-8 inches), the calculator determines the total number of biscuits needed and then divides the available length evenly between them to give you a precise on-center measurement.

Example 1: 36-inch tabletop edge glue-up.
Board 36″, ends held 3″ in. Available length is 36 − (2 × 3) = 30″. Count = floor(30 ÷ 8) + 1 = 4 biscuits, and the 30″ is split evenly into 3 gaps of 10″ on center, starting 3″ from each end. Four #20 biscuits keep a long glue-up from stair-stepping.

Example 2: 24-inch cabinet side, #10 biscuits.
With 2.5″ end spacing, available = 24 − 5 = 19″. Count = floor(19 ÷ 8) + 1 = 3, giving 9.5″ on center. For a panel glue-up whose only job is alignment, three biscuits are plenty — adding more just wastes slots and glue time.

• Over-biscuiting an edge joint. On a straight glue edge the glue, not the biscuits, carries the strength. Extra biscuits only add alignment, so stop at what keeps the boards flush.
• Slots too close to the ends. Placing a biscuit within about 2 inches of the board end risks blowing out the end grain. Keep the first slot 3 to 4 inches in, which is exactly the end-spacing input here.
• Cutting mating slots off the fence. If the two boards aren't registered the same way against the tool's fence, the slots won't line up. Mark centers on one board and transfer with a square.
• Ignoring biscuit size vs. thickness. A #20 in half-inch stock cuts so deep the slot nearly breaks through. Match the biscuit number to the material thickness.

"I treat biscuits as clamp-aid, not structure. For a flat panel glue-up I set spacing around 8 to 10 inches — just enough so the boards can't ride up when I tighten the clamps. Where a joint really sees load, like a mitered corner, that's when I add more and lean on the glue." — Cabinetmaker

"Dry-fit every slot before you squeeze up. Drop the biscuits in dry, run the boards together, and check the faces for flush. Once glue is in the slots you have minutes, not hours, to fix a mismatched center."

• Biscuit: A small, compressed piece of wood (usually beech) that, when glued into a slot, swells to create a tight, strong joint.
• Biscuit Joiner: A power tool that cuts crescent-shaped slots (or 'mouths') into the edges of boards to accept a biscuit.
• On-Center Spacing: The measurement from the center of one biscuit slot to the center of the next.
• End Spacing: The distance from the end of the board to the center of the first biscuit slot.