Vinyl Siding Calculator
Estimate vinyl siding for a whole house. Enter the perimeter and wall height in feet, add gable dimensions and total window/door area in square feet, and get net wall area, squares with waste, and boxes to order.
Example: with House perimeter (ft) 140 · Wall height to eaves (ft) 9 · Number of gables 2 · Gable width (ft) 30 · Gable height at peak (ft) 7 → Net wall area: 1,350 sq ft net wall area.
- Siding to buy14.9 squares (1,485 sq ft with waste)
- Boxes8 boxes (2 squares per box)
Computed by the calculator below using its default values. Change any input to see your own numbers.
Wall area = perimeter × height + gable triangles (½ × width × height each) − openings. Siding is sold in squares of 100 sq ft; a typical box holds 2 squares.
How siding is measured and sold
Siding trades in squares — one square is 100 sq ft of wall. To get there, measure the distance around the house (perimeter), multiply by the wall height from foundation to eaves, then add each gable as a triangle: half its width times its height at the peak. Subtract window and door area, since a typical house gives back 100-200 sq ft in openings.
Vinyl panels come boxed, usually 2 squares (200 sq ft) per carton for standard double-4 and double-5 profiles. Boxes here are rounded up from the waste-included square count, because you cannot buy a partial carton.
Choosing the waste factor
Ten percent is the standard allowance for a simple rectangular house — it covers end cuts, lock damage, and the offcuts at windows. Go to 15% for hips, dormers, bays, or diagonal-heavy designs, and consider more if the panel has a pattern you must match. Trim pieces (J-channel, starter strip, corner posts, utility trim) are ordered separately by linear foot and are not included in this count.
How it’s calculated
Net wall area = perimeter × wall height + gables × (½ × gable width × gable height) − opening area. Area with waste = net area × (1 + waste%/100). Squares = area with waste ÷ 100; boxes = area with waste ÷ 200 sq ft per box, rounded up.
Assumes rectangular walls and simple triangular gables; complex elevations (bays, dormers, angled walls) need their sections measured and added to the perimeter figure manually.
Waste factors that estimators actually use
| House shape | Waste |
|---|---|
| Simple rectangle, gable roof | 10% |
| T- or L-shaped, a few dormers | 12-15% |
| Hips, bays, turrets, pattern matching | 15-20% |
Standard siding-estimating convention; matches manufacturer installation guides (e.g., VSI Vinyl Siding Installation Manual guidance on ordering).
Common mistakes
- Measuring wall length wall-by-wall and missing offsets — walk the full perimeter; every jog adds siding.
- Subtracting every small window. Skip openings under about 10 sq ft; the offcuts around them are rarely reusable.
- Forgetting gables — two 30 ft gables at 7 ft add over 200 sq ft, roughly two full squares.
- Ordering trim as an afterthought; starter strip and J-channel run the entire perimeter and every opening, and shortages stop the job.
Frequently asked questions
What formula does a vinyl siding estimate use?
Net area = perimeter × height + ½ × width × height for each gable, minus window and door area. Divide the waste-included area by 100 to get squares, the unit siding is priced in.
What is a square of siding?
100 square feet of wall coverage. A typical vinyl carton holds two squares, so an 1,485 sq ft job needs 8 boxes.
Do I subtract windows and doors?
Yes, for a whole-house estimate — openings commonly total 100-200 sq ft. But leave small windows in as cushion, and never subtract openings and then skip the waste factor; the two serve different purposes.
How much waste should I add for vinyl siding?
10% on a simple house, 15% or more with dormers, hips, or bays. Waste comes from end cuts at corners and openings, and from matching panel locks, not from sloppy work.
Does this include J-channel, starter strip, and corners?
No — trim and accessories are linear-foot items ordered separately. Measure the perimeter for starter strip, each opening's sides and top for J-channel, and each outside/inside corner's height for posts.