Garden Bench Calculator — Timber Quantities & Dimensions

This calculator estimates the timber needed for a traditional garden bench with seat slats, optional backrest, legs, and structural braces.

Slat calculation

Seat slats = ceil(Seat depth / (Slat width + Slat gap))

Back slats = ceil(Backrest height / (Slat width + Slat gap))

Slat gap (default 5mm) and backrest height (default 400mm) are editable under Advanced Options, so the formula uses your values, not fixed constants.

Timber total

Total timber includes: all slats at bench length, 4 legs, 2 armrests at seat depth, and 3 cross braces at bench length. All measurements are converted to linear metres, then multiplied by your waste factor (default 1.1 = 10%).

For a conservative order, every leg is costed at full back-leg height (seat height + backrest height + 50mm clearance). On a bench with a backrest only the two rear legs actually reach the top of the back, so this slightly over-orders leg timber — useful headroom for cuts and waste rather than a shortfall.