Calculator
Example Data Table
| Project | Length | Left Return | Right Return | Eave Sides | Waste % | Board Length | Required Trim | Boards |
|---|---|---|---|---|---|---|---|---|
| Small Gable Home | 12.00 m | 0.25 m | 0.25 m | 2 | 10% | 6.00 m | 27.50 m | 5 |
| Hip Roof Garage | 16.00 ft | 0.75 ft | 0.75 ft | 4 | 8% | 8.00 ft | 75.60 ft | 10 |
| Shed Roof Porch | 9.00 m | 0.30 m | 0.30 m | 1 | 5% | 4.00 m | 10.08 m | 3 |
Formula Used
Per Side Eave Length = Building Length + Left Return + Right Return
Base Total Eave = Per Side Eave Length × Number of Eave Sides
Waste Length = Base Total Eave × (Waste % ÷ 100)
Required Trim/Fascia = Base Total Eave + Waste Length
Boards Required = Ceiling(Required Trim ÷ Stock Board Length)
This method is practical for fascia, trim, drip-edge planning, and ordering linear materials along exposed roof edges.
How to Use This Calculator
- Choose the roof type or keep a custom layout.
- Enter the main building length in meters or feet.
- Add left and right returns for any end overhangs.
- Set the number of eave sides you want included.
- Enter a waste percentage for cuts, joins, and site loss.
- Enter your stock board length to estimate piece count.
- Press the calculate button to show results above the form.
- Use the CSV and PDF buttons to export the result summary.
FAQs
1. What is eave length?
Eave length is the roof edge that projects past the wall. In this calculator, one side equals the main length plus both end allowances.
2. Why do left and right returns matter?
Returns add extra linear length at the ends. Including them prevents under-ordering fascia, trim, or drip-edge material for roof edge finishes.
3. What does the waste percentage cover?
Waste covers cuts, offcuts, bad joints, corner trimming, and minor jobsite damage. A small allowance usually improves purchasing accuracy.
4. How many eave sides should I enter?
A simple shed roof often has one eave side. Many gable roofs use two. Hip roofs often need four, depending on design.
5. Does this help with fascia ordering?
Yes. The required trim result gives a practical linear estimate for fascia or similar edge materials after waste is included.
6. What stock board length should I use?
Use the actual supplier length of the fascia, trim board, or metal piece you plan to buy. The board count updates from that value.
7. Can I switch between meters and feet?
Yes. Enter values in your chosen unit. The calculator also reports the required trim in both meters and feet.
8. Does this calculator find roof area?
No. It estimates linear eave-related length, not roof surface area. Use a separate roofing area tool for sheet coverage calculations.