Siding Calculator
Calculate siding squares and boxes from wall perimeter, height and gables, less doors and windows, plus starter strip, J-channel, corner posts and soffit.
Net area = (perimeter × wall height) + gable triangles − door and window openings, and a square is 100 sq ft, the unit siding has always been sold in. Vinyl comes two squares to a box; lap products are ordered by length, so the plank footage is net area ÷ the exposure to the weather. Starter strip runs the bottom of the walls, J-channel wraps every opening, and corner posts are one wall height each. Complex elevations, dormers and stepped foundations all add waste, so 10% is a floor rather than a ceiling. Estimates only.
What is the Siding Calculator?
The ByteTools Siding Calculator turns a house's elevations into a siding order. Enter the wall perimeter and height, add the gable ends, deduct the doors and windows, and it returns the net area in squares — the 100 square foot unit siding has always been sold in — plus the boxes or planks that represents at your product's exposure.
- Net area from perimeter × height plus gable triangles, less every opening
- Squares, boxes at two squares each, and plank counts from the exposure to the weather
- Starter strip, J-channel, corner posts, soffit area and fascia length
- Presets for vinyl, fibre cement, wood lap, board and batten and shakes
- Editable waste allowance and a cost estimate per square
- Runs entirely in your browser with nothing uploaded
How to use the Siding Calculator
- 1
Choose imperial or metric and enter the total wall perimeter and the height to the eaves.
- 2
Pick a siding product to set a typical exposure, then adjust the exposure, plank length and waste allowance.
- 3
Enter the gable ends with their base width and rise to the ridge.
- 4
Enter the doors and windows to deduct, and the number of outside and inside corners.
- 5
Tick the soffit box and set its width, then read the squares, boxes, planks and trim lengths.
About the Siding Calculator
The ByteTools Siding Calculator turns a house's elevations into a siding order. Enter the wall perimeter and height, add the gable ends, deduct the doors and windows, and it returns the net area in squares — the 100 square foot unit siding has always been sold in — plus the boxes or planks that represents at your product's exposure.
It also counts the trim that gets forgotten until the van is already loaded: starter strip along the bottom of every wall, J-channel around every opening, corner posts at one wall height each, and the soffit and fascia around the eaves. Vinyl comes two squares to a box, while lap products are ordered by length, so both routes are shown.
All the arithmetic happens in your browser and nothing is uploaded. Complex elevations, dormers, stepped foundations and bay windows all add waste beyond the 10% default, so treat that figure as a floor. Estimates only — measure each elevation separately if the house is anything other than a plain box.
Frequently asked questions
How many squares of siding do I need?
Divide the net wall area by 100. A house with 140 ft of perimeter and 9 ft walls has 1,260 sq ft; add two 120 sq ft gables and deduct a couple of doors and ten windows and you land near 1,340 sq ft — about 14.7 squares once a 10% waste allowance is added, or eight boxes of vinyl.
How many square feet is a box of vinyl siding?
A standard box of vinyl siding covers two squares, or 200 square feet. That is the figure this calculator uses, so a 13 square job comes out at seven boxes. Fibre cement and wood lap are sold by the plank instead, which is why the tool also gives you a plank count.
How do I calculate the area of a gable end?
A gable is a triangle: half the base width times the rise to the ridge. A 30 ft wide gable rising 8 ft is 0.5 × 30 × 8 = 120 sq ft. Enter the number of gables and their dimensions and the calculator adds them to the wall area for you.
What is siding exposure?
The exposure is the visible face height of one course once the next course laps over it — 4 in on single-4 vinyl, about 6 3/4 in on 8 in fibre cement lap. Plank footage is net area divided by the exposure, so a smaller exposure means noticeably more material.
How much waste should I allow for siding?
Ten per cent on a simple rectangular house, and 15% or more where there are lots of gables, dormers, windows or angled cuts. Every opening you deduct also creates offcuts that usually cannot be reused, so the deduction and the waste allowance partly cancel out.
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