Dado Rail Calculator

This calculator determines the total length of dado rail needed, the number of standard lengths to buy, mitre joint count, adhesive and pin nails for your room.

Rail length

Total rail = Room perimeter − Door openings. Each standard UK internal door leaf is 762mm wide, and the calculator deducts that bare 762mm per door. This is deliberately conservative: the rail actually butts into the architrave, so the real gap is a little wider (around 900mm once you add an architrave each side), meaning you will have a small amount of rail to spare rather than too little.

Lengths to buy

Lengths = ceil(Total rail / Standard length). Standard dado rail comes in 2.4m or 3.0m lengths. Allow extra for mitre cuts at corners, as each mitre wastes a small amount.

Mitre joints

Each internal and external corner requires a mitre joint (two angled cuts meeting at the corner). Internal corners can be coped for a tighter fit on older walls. External corners must always be mitred.

Adhesive and fixings

• Grab adhesive: roughly 1 tube per 8m of rail (a typical estimate for a zig-zag bead — adjust to your product)
• Pin nails: 1 per 300mm to hold rail while adhesive cures

Standard height

Dado rail is traditionally fixed at 900mm to 1000mm from the finished floor level — about two-fifths of the way up a standard 2.4m wall. A common proportional rule is wall height ÷ 5 × 2, which puts the rail at roughly 960mm in a 2.4m room.