Kerf and recovery: where does the log go?

Recovery

Recovery % = lumber volume / log volume × 100

If 100 m³ of logs yield 48 m³ of lumber, recovery is 48 % and 52 % becomes chips, sawdust, bark and other residue. Residue is not simply waste: it is usually sold or used as energy.

Kerf

Every saw cut turns a strip of wood into sawdust. The share of material lost to kerf in a stack of boards is:

Kerf share % = kerf / (board thickness + kerf) × 100

With a 3.5 mm kerf and 25 mm boards, about 12.3 % of the sawn height becomes sawdust. Thinner boards or a wider kerf raise this share.

Other losses

Slabs and edgings (the rounded outer parts), trimming to length and removing defects also reduce recovery. A real sawmill measures recovery over a period of production, not for a single log.

The Kerf loss calculator and the Log cutting simulator show how board thickness and kerf affect yield. The simulator is a simplified geometric model, not a prediction for a particular saw.