All the calculations heroAll The Calculations

construction calculator

Door & Window Trim Calculator

Estimate casing trim for doors and windows, including waste buffers and board counts.

Results

Linear feet of trim
100.00 ft
Linear feet incl. waste
110.00 ft
8 ft boards needed
14.00

How to use this calculator

  1. Enter counts and dimensions for windows and doors.
  2. We compute total casing perimeter for all openings.
  3. Apply waste percentage for cuts/defects and divide by 8 ft to estimate board count.

Inputs explained

Windows/Doors
Number of openings to trim.
Width/Height
Opening dimensions in feet; casing wraps the full perimeter.
Waste allowance
Extra percentage for miter cuts, pattern matching, and damaged stock.

How it works

Each opening uses the perimeter formula: 2 × (width + height). We multiply by the count of windows and doors.

Waste allowance (default 10%) adds extra footage for miter cuts, damaged boards, and pattern matching.

We divide the waste-adjusted total by 8 ft to estimate how many standard sticks you need, rounding up.

Formula

Window trim = windows × 2(Ww + Wh)
Door trim = doors × 2(Dw + Dh)
Total = window trim + door trim
Waste total = Total × (1 + waste %)
Boards = Waste total ÷ 8

When to use it

  • Ordering casing trim for multiple doors and windows at once.
  • Estimating waste when pattern matching or painting on-site.
  • Comparing board counts if using different stock lengths (8 ft vs 16 ft).

Tips & cautions

  • Measure actual openings on site—plan sizes can differ after framing.
  • Increase waste for elaborate profiles or lots of tight miters.
  • If using 16 ft sticks, divide the waste-adjusted footage by 16 instead of 8.
  • Assumes rectangular openings; arched or custom shapes need manual adjustments.
  • Board count assumes 8 ft stock—adjust if your supplier differs.
  • Does not include plinths or rosettes; add length if your design needs them.

Worked examples

4 windows (3×4.5 ft) + 2 doors (3×7 ft) with 10% waste

  • Base trim = 100 ft
  • Waste total ≈ 110 ft
  • Boards needed ≈ 14

6 windows + 3 doors with 5% waste

  • Adjust the waste percentage down if you’re confident in your cuts.

Deep dive

This trim calculator totals window and door casing footage, adds waste, and estimates 8 ft board counts. Enter opening counts/dimensions and waste % to size your trim order before installation.

Adjust waste for complex miters or pattern matching, and change the board length if you buy 10/12/16 ft stock.

FAQs

Does this include baseboards?
No. Use the baseboard calculator for perimeter trim; this tool is just for casing openings.
What if trim comes in 16 ft lengths?
Divide the waste-adjusted total by 16 instead of 8 to estimate pieces for longer stock.

Related calculators

construction

Concrete Volume Calculator

Estimate cubic yards, cubic feet, and bag counts for slabs, footings, and post holes.

construction

Paint Coverage Calculator

Estimate gallons of paint needed based on wall area, coats, and coverage rate.

construction

Tile Calculator

Determine tile counts and total area including waste.

construction

Gravel Volume Calculator

Estimate cubic yards and tons of gravel required for driveways, pads, or drainage projects.

Always verify opening sizes on site and buy a little extra for callbacks or future touch-ups.