Trim & Molding Calculator
Estimate project quantities from your measurements. Confirm technical requirements before making purchases.
Calculate your estimate
Preliminary planning only. Actual requirements depend on site conditions and product specifications.
Measure the perimeter that receives trim
- Enter the rectangular room’s length and width in feet. The calculator uses all four sides to build the perimeter.
- Enter the combined door-opening width only where this trim is omitted. Leave deductions at zero for a continuous run.
- Set a cutting allowance and select Calculate for linear feet. Measure casing around doors and windows separately.
Trim & Molding Calculator: formula and assumptions
Trim length = [2 × (room length + room width) − door deductions] × (1 + waste ÷ 100).
Worked calculation
A 16 × 12 ft room has 56 ft perimeter. Subtracting 6 ft and adding 10% waste gives 55.0 linear ft.
What this estimate includes
Use deductions only for trim omitted at doors. Equal deductions give zero net trim; deductions above the perimeter are invalid. Windows, crown molding and stock-length optimization require separate measurement.
Planning details that change the estimate
The output is a length takeoff rather than a count of stock pieces. A room may need more purchased length than the total because a long wall cannot always be assembled from leftover short pieces. Sketch the wall runs and match them to available stock lengths, allowing for miters and other cuts. Baseboard, crown molding and casing have different paths; do not apply a baseboard door deduction to crown molding that continues above the door.
Trim & Molding Calculator FAQs
Should I deduct doors when estimating crown molding?
Only if the molding is actually absent along that run. Crown often continues above a door, so a baseboard deduction may not apply.
Does this include door and window casing?
No. Casing follows each opening’s sides and head rather than the room perimeter. Measure those runs separately.
How many 8-foot pieces should I buy?
Dividing by eight gives only a theoretical minimum. Check each wall run and the cutting plan before rounding to whole stock pieces.
Can deductions exceed the room perimeter?
No. That indicates an inconsistent takeoff. Equal deductions produce zero net trim; a larger deduction is rejected.
Continue planning this project
Estimate room surfaces with the Square Footage Calculator and coatings with the Paint Calculator. Use the Wall Stud Calculator if the trim work is part of a framing project.
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