Calculator
Example data table
| Scenario | Perimeter | Waste | Stock length | Pieces | Miter / Bevel (38°, 90° corner) |
|---|---|---|---|---|---|
| Living room (rect.) | 56 ft | 10% | 12 ft | 6 | ≈ 31.62° / 33.86° |
| Hallway | 38 ft | 12% | 8 ft | 6 | ≈ 31.62° / 33.86° |
| Bedroom | 44 ft | 8% | 16 ft | 3 | ≈ 31.62° / 33.86° |
These examples assume standard 90° corners and a 38° spring angle.
Formula used
Material length is estimated from perimeter, minus omitted segments, plus any extra allowance, then adjusted by waste:
- Net = max(Perimeter − Omit, 0) + Extra
- Total = Net × (1 + Waste%/100)
- Pieces = ceil(Total / StockLength)
Compound cut settings (molding laid flat) use the spring angle and the corner angle between walls. Let WALL = CornerAngle/2. Then:
- tan(Miter) = sin(Spring) / tan(WALL)
- sin(Bevel) = cos(Spring) × cos(WALL)
Tip: for a 90° corner, WALL = 45°. For a 38° spring, the calculator returns about 31.62° miter and 33.86° bevel.
How to use this calculator
- Choose units and your perimeter mode.
- Enter room dimensions or a custom perimeter total.
- Add any omitted length and a small extra allowance.
- Set a waste factor, stock length, and pricing method.
- Enter corner and spring angles for accurate saw settings.
- Click Calculate, then download CSV or PDF if needed.
Professional notes for crown molding takeoffs
1) Measure the true run, not the room footprint
Crown rarely follows every wall. Door casings, cabinets, beams, and open returns can remove several feet from the run. Treat the perimeter as your starting data, then subtract omitted segments and add a small allowance for returns and test cuts in advance.
2) Waste is driven by corners and learning cuts
A typical field range is 8–15% waste. Simple rectangles with long, clean runs may land near 8–10%, while rooms with many short pieces or multiple outside corners often need 12–15%. Add more if you are matching grain or painting after install.
3) Stock length changes the board count
Using 16‑ft stock instead of 12‑ft can reduce joints, but it may increase leftover if your runs are short. This calculator converts the total required length into a piece count using ceil(Total / StockLength), so you can compare 8, 12, and 16 quickly.
4) Corner angle matters in older construction
Not every corner is a perfect 90°. A corner that is 88° or 92° changes the half‑angle (WALL = Corner/2), which shifts both miter and bevel settings. Measuring corners and entering the real angle can reduce visible gaps and rework.
5) Spring angle is a product property
Common profiles are 38° and 45° spring angles, but confirm the manufacturer’s spec or measure the angle between the back surfaces. The spring angle controls how the profile nests between wall and ceiling, and it directly impacts compound settings.
6) Saw settings: flat method output
The miter and bevel results are for cutting crown laid flat on a compound saw. For a standard 90° corner (WALL = 45°) and a 38° spring, the calculator returns about 31.62° miter and 33.86° bevel. Always make a scrap confirmation cut before production.
7) Plan joints where they disappear
Place scarf joints above doors or near less visible walls. Long runs may need multiple pieces, and extra allowance helps you shift joints away from focal points. Prime and seal end grain to improve paint finish and reduce seasonal separation.
8) Use cost inputs for bids and material staging
Pricing by linear length supports quick estimating, while pricing by piece aligns with many supplier quotes. Export the CSV or PDF to attach a cut‑list summary, document assumptions (waste, stock length, corner counts), and keep crews staged.
FAQs
1) What is crown molding “spring angle”?
The spring angle is the angle between the molding’s back surfaces and the wall/ceiling when installed. Common values are 38° and 45°, and it drives compound miter and bevel settings.
2) Should I measure each wall or use a rectangle?
Use rectangle mode for clean, four‑wall rooms. Use custom perimeter for bump‑outs, open areas, partial runs, or when some walls are excluded. Custom perimeter usually reduces ordering errors.
3) How much waste should I enter?
Start with 10% for standard rooms. Increase to 12–15% for many corners, short pieces, or first‑time installs. Decrease toward 8% for long, simple runs with experienced cutting.
4) Why do my angles differ from a printed saw chart?
Charts assume exact corner and spring angles. If your corner is not 90° or your profile is not the listed spring angle, the correct settings shift. Measuring the corner angle usually resolves the mismatch.
5) Do inside and outside corner counts change the math?
The length estimate is driven by total run and waste, not counts directly. However, corner counts are practical job data that support planning waste, staging pieces, and noting where coping or returns are needed.
6) What if I’m coping instead of mitering inside corners?
You can still use the length and piece count outputs. Coping typically reduces visible gaps but still needs extra scrap for test fits. Keep waste near 10–12% unless you are highly experienced.
7) How do I handle vaulted ceilings or angled walls?
Vaults often require segmented runs and additional setup cuts. Measure the actual run line, enter a higher waste factor, and test the profile placement. For complex geometry, break the room into smaller sections and estimate separately.
Accurate planning saves time, money, and messy recuts always.