Vinyl Siding Calculator
Estimate how much vinyl siding you need for your house. Enter the length and height of your walls, the gable ends and the number of windows and doors, and this vinyl siding calculator shows siding squares, boxes and panels, plus starter strip, J-channel and corner posts.
Your results will appear here.
How to use the vinyl siding calculator
- Add up the wall lengths you plan to side. For a simple rectangular house, this is the perimeter: a 40 x 40 ft house is 160 ft.
- Enter the wall height from the foundation or starter line up to the eaves.
- Add the gable ends. Enter how many there are, the width at the base and the height from the base to the peak.
- Count windows, doors and corners. The calculator subtracts standard openings and estimates the trim around them.
- Choose the siding profile and box coverage, then set a waste allowance. About 10% is typical for a simple house; use more for many corners and gables.
Vinyl siding formula
Wall area = Wall length × Wall height
Gable area = Number of gables × Width × Height ÷ 2
Net area = Wall area + Gable area − Windows × 15 sq ft − Doors × 21 sq ft
Squares = Net area × (1 + Waste %) ÷ 100
Worked example
A 40 x 40 ft house has 9 ft walls, two gable ends 40 ft wide and 8 ft high, 12 windows, 2 doors and 4 outside corners. With 10% waste:
- Walls: 160 × 9 = 1,440 sq ft
- Gables: 2 × 40 × 8 ÷ 2 = 320 sq ft
- Openings: 12 × 15 + 2 × 21 = 222 sq ft
- Net area: 1,440 + 320 − 222 = 1,538 sq ft
- With 10% waste: 1,691.8 sq ft = 17 squares, or 9 boxes at 200 sq ft per box
- Double 4 in panels (8 sq ft each): 212 panels
- Trim: 14 pieces of starter strip, 20 pieces of J-channel and 4 outside corner posts
Siding profiles and panel coverage
| Profile | Exposure per panel | Coverage per 12 ft panel |
|---|---|---|
| Double 4 in (clapboard) | 8 in | 8 sq ft |
| Dutch lap 4.5 in | 9 in | 9 sq ft |
| Double 5 in | 10 in | 10 sq ft |
Siding is priced and sold by the “square”, which is 100 sq ft of wall coverage. Most boxes hold about two squares, but the exact number of panels per box varies by brand and profile, so check the label before you order.
How the trim is estimated
- Starter strip: runs along the bottom of every wall, sold in 12 ft pieces.
- J-channel: about 16 linear ft around each 3 x 5 ft window and 17 linear ft around each 3 x 7 ft door, plus 10%, in 12 ft 6 in pieces.
- Corner posts: one 10 ft post per corner, or two stacked posts when the wall is taller than 10 ft.
Soffit, fascia, gable trim and undersill trim depend on the roofline and window details, so measure them separately.
Tips for ordering vinyl siding
- Measure large openings separately. Patio doors, bay windows and garage doors are much bigger than the standard openings used here. Subtract their actual size.
- Allow for gables and dormers. Triangles and steep cuts create more waste than flat walls. Raise the waste allowance to 12% to 15% for a complex house.
- Buy from one batch. Order enough at once so the color matches. A box or two left over is useful for future repairs.
- Follow the installation guide. Vinyl expands and contracts with temperature, so nail it loosely and leave gaps at channels as the manufacturer directs.
Frequently asked questions
How many squares of siding do I need?
Divide the net wall area, after subtracting windows and doors and adding gables, by 100, and then add 10% to 15% for waste. A typical 1,500 sq ft wall area needs about 17 squares.
How much is a square of siding?
A square is 100 sq ft of wall coverage. It is the standard unit for pricing and ordering siding.
How many boxes of vinyl siding do I need?
Most boxes cover about 200 sq ft, or two squares. Divide the area you need, including waste, by the coverage printed on the box and round up.
Should I subtract windows and doors?
Yes, but only standard openings. Many installers subtract windows and doors and then add waste back, because cutting around openings creates offcuts.
How much waste should I allow for siding?
About 10% for a simple rectangular house, and 12% to 15% for houses with many corners, gables, dormers or bump-outs.
Sources and methodology
The formulas on this page were written and checked by the HomeQuantly Team against the worked examples shown above. Results are estimates for planning; always confirm measurements on site before you buy materials.