Cornice Board Size Calculator

Measure once, build a crisp cornice for gardens. Adjust depth, returns, and lining for control. Print or export results, then cut with confidence today.

Enter Measurements
Use consistent units and measure the finished window span.
* required
The calculator converts fabric length to yd or m.
Visible span you want the cornice to cover.
Extra coverage beyond the window edges.
How far the cornice wraps to the left wall.
How far the cornice wraps to the right wall.
Distance from wall to the front face.
Visible height of the cornice front.
Choose 4-sided if you want a bottom return.
Used only for 4-sided builds.
Advanced Options
Adds a small corner buffer to returns.
Per edge for hems or stapled folds.
Extra for padding and wrap-around.
Space for garden hardware or brackets.
Exclude selvage if you won’t use it.
Rounds length up to the next repeat.
Covers trimming, alignment, and mistakes.
Example Data Table
Sample inputs and outputs to sanity-check your measurements.
Scenario Window Overlap Returns Depth Height Face length Top length
Small garden window 36 in 2 in 3/3 in 4 in 8 in 40 in 46 in
Wide span 72 in 3 in 4/4 in 5 in 10 in 78 in 86 in
Deep projection 60 in 2 in 5/5 in 7 in 9 in 64 in 74 in
Formula Used
How to Use This Calculator
  1. Select your unit system and measure the window span.
  2. Add side overlap for a fuller, more finished look.
  3. Enter returns if the cornice wraps to side walls.
  4. Set depth to clear garden hardware and brackets.
  5. Choose 3-sided or 4-sided, then calculate.
  6. Use the cut list and fabric estimate to plan materials.
  7. Export CSV or PDF to keep your build notes.

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Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.