Moulding & Trim Calculator — Linear feet
Linear feet of baseboard, crown moulding, chair rail and door / window casing for any room — with 10% mitre waste built in.
Quick answer
Quick rule: baseboard = (room perimeter − door widths) × 1.10. Crown moulding = perimeter × 1.10 (no door deduction). Casing = (door height × 2 + door width) × number of doors × 1.10.
Room details
Linear feet needed
50ft
Baseboard for 12×12 ft room
Room perimeter48 ft
Baseboard50 ft
Crown moulding53 ft
Chair rail50 ft
Door casing (3 sides)19 ft
Window casing (4 sides)18 ft
How moulding linear feet are calculated
Each type of moulding follows a slightly different rule. The base unit is always the room perimeter (2 × length + 2 × width), then you adjust for openings and add waste for mitre corners.
Baseboard: (perimeter − door widths) × waste%
Crown: perimeter × waste%
Door casing: (door height × 2 + door width) × number of doors × waste%
Window casing: (window height × 2 + window width × 2) × number of windows × waste%
Crown: perimeter × waste%
Door casing: (door height × 2 + door width) × number of doors × waste%
Window casing: (window height × 2 + window width × 2) × number of windows × waste%
Moulding types & what they cover
| Type | Where it goes | Door deduction? |
|---|---|---|
| Baseboard | Floor-to-wall joint, all walls | Yes — subtract door widths |
| Crown moulding | Wall-to-ceiling joint, all walls | No — runs continuous above doors |
| Chair rail | Mid-wall, ~32–36" from floor | Yes — subtract door widths |
| Door casing | 3 sides of each door (2 verticals + 1 horizontal) | — |
| Window casing | 4 sides of each window | — |
| Picture rail | Mid-to-upper wall, ~12" below ceiling | Optional |
Standard moulding heights / sizes
- Baseboard: 4" – 6" tall in standard rooms, 8" – 10" in tall-ceiling rooms.
- Crown moulding: 3" – 6" projection from wall, scaled to ceiling height.
- Chair rail: mounted at 32" – 36" from floor (back-of-chair height).
- Door & window casing: 2" – 3.5" wide profiles are standard.
Tips for installation
- Add 10–15% waste minimum — mitre cuts always have offcuts.
- Buy from one batch — wood and primed MDF can have slight colour / finish variation.
- Pre-prime backside before installing to prevent moisture warping.
- Use a coping joint at inside corners instead of mitre — looks cleaner over time.
Frequently asked questions
How do I calculate baseboard for a room?
Add up the perimeter of the room, subtract door widths (no baseboard at doors), then add 10% for mitre waste. A 12×12 ft room with one 3 ft door needs (48 − 3) × 1.10 = ~50 linear feet of baseboard.
How much crown moulding for a 12x12 room?
A 12×12 ft room has a 48 ft perimeter at the ceiling. Crown moulding has no door deductions (it runs continuously). Add 10% for mitre cuts: 48 × 1.10 = ~53 linear feet.
Should I add waste for moulding?
Yes — always add 10% for straight runs and 15% for rooms with many corners or short walls. Mitre cuts at corners create waste, and you'll want spare pieces for any installation errors.
What size baseboard for an 8 ft ceiling?
Standard 4–6 inch baseboard works for 8 ft ceilings. For 9 ft ceilings, jump to 6–8 inch. For 10 ft ceilings or taller, use 8–10 inch baseboards to keep proportions balanced.
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