Roofing
Soffit & Fascia Calculator
Calculates linear metres of soffit and fascia around the eaves
Updated June 26, 2026 · Live
What this tool does
Calculates the linear length of soffit and fascia needed around the eaves and gable edges, with the soffit panel area as a secondary figure.
Formula Used
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How the soffit & fascia calculator works
This calculator takes the total length of eaves and gable edges, adds 5% for corners and offcuts, and reports the linear run of fascia and soffit you need. It also works out the soffit panel area from the overhang depth so you can price vented soffit by the square as well.
Soffit and fascia basics
Fascia is the board (or aluminum/vinyl cover) that runs along the edge of the roof and carries the eavestrough. Soffit is the panel that closes in the underside of the overhang from the fascia back to the wall; vented soffit lets the attic draw intake air. Together they finish and protect the roofline.
Vented vs solid soffit
In Canada most eaves use vented soffit to feed attic ventilation, with solid soffit on gable ends and porch ceilings. If you are matching attic intake to a ventilation calculation, count how much of your soffit run is vented.
What this tool does not do
It estimates linear quantity and panel area only. It does not size attic ventilation, specify trim and J-channel, or detail the fascia-to-eavestrough connection — confirm those with your supplier or installer.
Adjusting the defaults
Every input is editable. Enter your own perimeter, overhang depth and price and the length, area and cost recalculate instantly.
On-site considerations
Run a straight, level fascia first — it carries the eavestrough, so any sag shows up as standing water later. Hold vented soffit clear at the wall so it can actually draw air, and finish the inside and outside corners with the matching trim and J-channel. Measure gable returns separately; they carry fascia but usually solid soffit.
Using this alongside other BuildMetricLab tools
Pair this with the eavestrough, roof vent and attic baffle calculators when redoing a roofline, and with the material cost calculator to price the soffit, fascia and trim. Every BuildMetricLab tool runs in your browser — no sign-up, no data sent anywhere, and every formula is shown so you can audit the math.
Sources & methodology
Calculates the run as the eaves and gable perimeter plus 5% for corners and offcuts, and reports the soffit panel area from the overhang depth. Every result is calculated from the values you enter, and all inputs are editable.
Frequently asked questions
Are soffit & fascia calculator results accurate enough to order materials?
Use them as a starting estimate only. Verifying the final quantity with your supplier or contractor before ordering is good practice — site conditions, wastage and cut-offs all affect the true figure.
What wastage percentage should I use?
The calculator defaults to the typical Canadian trade allowance for driveway & hard paving. Increase it for complex cuts, awkward shapes, or first-time DIY. The default wastage allowance reflects common trade practice; values lower than the default may underestimate offcuts.
Does this replace professional advice?
No. This tool is a planning estimator. For works that affect structure, the National Building Code (NBC), property-line or shared-wall, gas, electrics, drainage to a sewer, or similar, consult a suitably qualified professional.
Can I change the unit prices?
Yes — every price field is editable. Plug in your supplier's quote to get a total that matches your project.
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