How much siding do I need?
Measure each wall's length and height, add the triangular gables, and subtract windows and doors. Add waste and divide by 100. Siding is sold and priced by the square, which is 100 sq ft of wall.
Squares = (wall area + gable area − openings) × (1 + waste %) ÷ 100
Take a 40 × 30 ft house with 9 ft walls. The four walls are 2 × 40 × 9 + 2 × 30 × 9 = 1,260 sq ft. The two gables are 30 ft wide and 7.5 ft tall, so each is 30 × 7.5 ÷ 2 = 112.5 sq ft, or 225 sq ft together. That's 1,485 sq ft gross. Twelve windows at 15 sq ft and two doors at 20 sq ft take out 220 sq ft, leaving 1,265 sq ft net, or 12.7 squares. With 10% waste you need 13.9 squares.
In vinyl that's 7 boxes at 2 squares per box. In 8.25 in fiber cement lap at 7 in exposure it's 199 twelve-foot boards.
Siding coverage by type
| Siding | Sold as | Typical coverage |
|---|---|---|
| Vinyl, double 4 in or double 5 in | Boxes | 2 squares per box |
| Fiber cement lap, 8.25 in | 12 ft boards | 7 in exposure, 7 sq ft per board, 14.3 boards per square |
| Fiber cement lap, 6.25 in | 12 ft boards | 5 in exposure, 5 sq ft per board, 20 boards per square |
| Wood or engineered lap | Boards, often 16 ft | Exposure × length; check the product |
For lap siding, each board covers its exposure times its length. An 8.25 in plank laid at 7 in exposure on a 12 ft board covers 7 ÷ 12 × 12 = 7 sq ft. Check the manufacturer's exposure for your product and enter it above.
Vinyl siding calculator
Vinyl is usually sold in cartons that cover 2 squares, though some profiles differ. Besides the panels you need starter strip along the bottom of each wall, J-channel around windows, doors and along the gable rakes, and corner posts. The calculator works out starter strip from the length of each rectangular wall. Enter your window and door trim and your corners as linear feet. A 3 × 4 ft window takes about 14 ft of J-channel.
Lap siding calculator
Pick fiber cement or other lap siding and set the exposure and board length. Corner boards are counted two per corner, one for each face. Fiber cement is heavy and slow to cut, so the labor default is higher than vinyl. Follow the manufacturer's nailing and clearance rules, since they affect the warranty.
Siding calculator cost
The shopping list prices every line, so the total is your material cost. Change any price to match your supplier. House wrap is counted on the gross wall area plus 10% for laps, because it goes on before the openings are cut. Nails default to about 1 lb per square for vinyl and 1.5 lb for fiber cement. Your nail length and spacing change that, so adjust it.
Siding calculator app
This calculator runs in your phone's browser, so you can walk the house and add each wall as you measure. Name each wall, and your inputs stay saved on your device.
Pricing a siding job
Siding contractors usually price by the square, with trim and tear-off on top. Switch to contractor mode to set your labor hours per square, rate and markup. Then send it with the estimate template.
Questions
How much siding do I need for a 1,500 sq ft house?
It depends on wall area, not floor area. A one-story 50 × 30 ft house with 9 ft walls has 1,440 sq ft of wall plus about 225 sq ft of gables at a 6/12 pitch. After 220 sq ft of windows and doors and 10% waste, that is about 15.9 squares.
How many squares are in a box of vinyl siding?
Most boxes of vinyl siding cover 2 squares, or 200 sq ft. Some profiles differ, so check the carton.
How many fiber cement boards are in a square?
About 14.3 boards of 8.25 in lap at 7 in exposure on 12 ft boards. At 5 in exposure for 6.25 in lap it's 20 boards.
How much waste should I add for siding?
Typically 10%. Use 15% for houses with many gables, corners or dormers.