Calculate how much soffit you need: enter eave length and overhang depth to get square feet, panels and fascia length, or plan soffit vent area.

Area result unit

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Soffit Formula

The following formula is used to calculate the area of a soffit:

A = L × W

Variables:

  • A is the area of the soffit
  • L is the length of the soffit
  • W is the width of the soffit

For a rectangular eave strip, area equals total eave length × horizontal overhang depth. Sum separate runs when depths differ. Whole panels = ceiling[area × (1 + waste percent / 100) / net installed coverage per panel]; a blank waste allowance means 0%. Area-based ordering can need extra panels for cuts, seams and unusable offcuts.

For ventilation planning, total NFVA in square inches = attic floor area in square feet × 144 / ratio. Lower intake NFVA = total NFVA × intake share / 100; continuous vent length in feet = intake NFVA / the product’s rated square inches of NFVA per foot. The 2024 IRC R806.2 baseline is 1:150. Its conditional 1:300 arrangement assigns 40–50% to upper ventilation and the balance to the bottom third; climate zones 6–8 also require the specified warm-side Class I or II vapor retarder. The default 50% lower intake is one planning split. Verify adopted local code, vent placement, adequate exhaust and clear airflow; gross soffit area is not a vent’s NFVA rating.

What is a Soffit?

A soffit is a component of a building’s architecture that is typically found on the underside of elements such as arches, balconies, or overhanging eaves. It serves both aesthetic and functional purposes. Aesthetically, it provides a finished look, hiding the underside of the roof overhang, the floor of a balcony, or the underside of a flight of stairs. Vented soffits can supply lower attic intake as part of a properly designed ventilation system; solid soffit area alone does not establish ventilation or moisture control. It is usually made from materials like wood, metal, or vinyl, which are chosen for their durability and resistance to weather conditions. The soffit can also house lighting or speakers for outdoor entertainment spaces.

How to Calculate Soffit?

The following steps outline how to calculate the Soffit.

  1. First, determine the length of the soffit (in inches).
  2. Next, determine the width of the soffit (in inches).
  3. Next, gather the formula from above: Soffit = Length x Width.
  4. Finally, calculate the Soffit.
  5. After inserting the values and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

Length (in inches) = 12

Width (in inches) = 6

Select inches for both length inputs: 12 × 6 = 72 square inches = 0.5 square feet. The calculator also accepts feet and metres and converts changed input units.