Wall & Ceiling
Dado Rail Calculator
Calculates linear metres or feet of dado rail for a room
Updated 13 May 2026 · Live
What this tool does
Calculates linear metres or feet of dado rail for a room.
Formula Used
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How the dado rail calculator works
This calculator estimates the length of dado rail a room needs. It takes the room perimeter, subtracts the width of any door openings the rail runs around, and adds a 5% allowance for cutting and mitres. It also shows an indicative cost from the price per metre you enter. A dado rail runs horizontally around a room, traditionally at about waist height, so the perimeter is the figure that sets the length.
Measuring the perimeter and openings
The perimeter is the total length of the walls the rail runs along — add every wall, including the returns into bays and alcoves. Door openings are subtracted because the rail stops at the architrave; the door-widths input is the combined width of those openings. Windows are usually left in, since most dado rails run below the sill and continue across the wall beneath.
Cutting allowance and mitres
The calculator adds 5% to the net run for offcuts and the mitres at internal and external corners. Long, simple rooms use close to the net length; rooms with many corners, bays or breaks consume a little more in mitre offcuts. Lengths bought slightly over each wall run keep the number of joints along a wall down.
What this tool does not do
It does not set out the rail height, the mitre angles, or the fixing method for your wall type. It does not replace a professional quote or factor regional pricing. Solid timber, MDF and duropolymer dado rails are fixed and finished differently, and the supplier’s data covers that.
On-site considerations
Dado rails are sold in fixed lengths, so the run is made up from several pieces with joints scarfed or mitred where lengths meet. A consistent height set from a level line around the room keeps the rail true where floors are uneven, and corners are usually mitred for a clean return.
Adjusting the defaults
Every input here is editable. Enter your own perimeter, door widths and price per metre, and the length and cost recalculate instantly. If a default does not match your room, your own numbers always take precedence.
Using this dado rail calculator alongside other BuildMetricLab tools
This calculator works best as part of a wider plan. Pair the length with our project contingency and labour-cost calculators to build a complete estimate before contacting a supplier. All BuildMetricLab tools run entirely in your browser — no sign-up, no data sent anywhere, and every formula is shown on-page so you can audit the maths.
Sources & methodology
Calculates linear metres or feet of dado rail for a room. Every result is calculated from the values you enter, and all inputs are editable.
Frequently asked questions
Are dado rail calculator results accurate enough to order materials?
Use them as a starting estimate only. Verifying the final quantity with your supplier or contractor before ordering is good practice — site conditions, wastage and cut-offs all affect the true figure.
What wastage percentage should I use?
This calculator adds a fixed 5% to the net run for corner mitres and offcuts, so there is no wastage field to set. Rooms with many corners or bays use a little more than a plain rectangular room; for those, a slightly longer perimeter or rounding the result up gives more margin.
Does this replace professional advice?
No. This tool is a planning estimator. For works that affect structure, Building Regulations, Party Wall, gas, electrics, drainage to a sewer, or similar, consult a suitably qualified professional.
Can I change the unit prices?
Yes — every price field is editable. Plug in your supplier's quote to get a total that matches your project.
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