How this calculator works
Add up the areas of all the walls (the perimeter times the wall height), add the gable triangles (half the base times the rise), then take off the openings. That is the area to cover. Add a margin for the cuts, divide by 100 and that is the number of squares: siding is sold by the square, which is 100 square feet.
Worked example: a house with a 140 ft perimeter, 9 ft walls and two 28 × 8 ft gables: 140 × 9 = 1,260 ft² of walls, plus 2 × ½ × 28 × 8 = 224 ft² of gables, so 1,484 ft². Minus 150 ft² of windows and doors, there are 1,334 ft² to cover. With 10% waste that is 1,467 ft², or 14.7 squares. Lap siding with 7 in of exposure and 12 ft pieces covers 7 ft² per piece, so you need 210 pieces.
Siding squares for typical single-story ranch houses (8 ft walls, 10% waste)
Hip roof, no gables, 120 ft² of windows and doors. Add gables and openings in the calculator for yours.
| Footprint | Perimeter | Siding to order |
|---|---|---|
| 24 × 32 ft | 112 ft | 8.5 squares |
| 28 × 40 ft | 136 ft | 10.6 squares |
| 30 × 50 ft | 160 ft | 12.8 squares |
| 40 × 60 ft | 200 ft | 16.3 squares |
Tips before you buy
- Order all of the siding at once, from the same batch. Colors can differ a little between production runs, and leftovers are useful for repairs.
- Measure each wall and add them up rather than guessing. A house that has many bump-outs or dormers needs more waste, up to 15%.
- Do not forget the trim: corner posts, J-channel around windows and doors, starter strip, soffit and fascia are bought by the foot, separately from the siding squares.
- A water-resistant barrier and flashing at windows, doors and the bottom of the wall matter more than the siding itself for keeping the wall dry.
- Allow vinyl siding to move with temperature. Nail loosely in the center of the slots, and do not drive nails tight.
- Siding is easier to cut and fit at a dry, mild temperature. Cold makes vinyl brittle.
Tools & materials for this project
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Frequently asked questions
How many squares of siding do I need?
Divide the wall area in square feet, with waste, by 100. A 1,334 ft² house with 10% waste needs 14.7 squares, so you would order 15.
What is a square of siding?
A square is 100 square feet of wall. Vinyl and fiber cement are often sold by the square, or by the piece, which the calculator also gives.
How much extra siding should I order?
About 10% for a simple house, and 15% for one with many angles, dormers or windows. Order 5% more again if you may want spares for later repairs.
How do I measure a gable?
It is a triangle: half of the base (the width of the wall at the bottom of the gable) times the height from the base to the peak.
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Related calculators & guides
Estimates only. Results assume standard materials and simple shapes. Supplier products vary, and the final call on quantity, structure and safety is yours. Check your local code and your supplier's guidance before ordering.