Siding Calculator
Siding squares from your wall area, minus windows and doors — the unit every siding product and quote is priced in.
Result
| Net wall area | |
| Squares before rounding |
Units & conversions used
Siding is sold by the square: 1 square = 100 ft² of wall coverage. Areas are in ft²; metric inputs convert at 1 m² = 10.7639 ft².
Formula & source
Squares = ⌈ net area × (1 + waste%) ÷ 100 ⌉
Source: selling siding by the square (100 ft²) is the industry-wide convention across vinyl, fiber cement and wood products, and contractor quotes are issued in the same unit. The waste allowance follows standard estimating practice for cuts around openings and at wall ends. Panels per square vary by profile and exposure — check your product's stated coverage per carton.
Worked example (you can verify by hand)
Input: 1,000 ft² of wall, 100 ft² of windows and doors, 10% waste.
- Net area: 1,000 − 100 = 900 ft²
- With 10% waste: 900 × 1.10 = 990 ft²
- Squares: 990 ÷ 100 = 9.9 → round up
Expected output: 10 squares to buy (net wall area 900 ft²).
Limitations — what this cannot do
- Squares only. It does not count J-channel, corner posts, starter strip, utility trim, soffit and fascia, fasteners or house wrap — those are ordered by the piece or roll, not by the square.
- Panels per square depends on the profile's exposure (a double-4 panel and a double-6 panel cover differently). Confirm the carton's coverage per square before ordering.
- Gable triangles must be measured into the total wall area yourself (½ × base × height each); forgetting gables is the most common under-order on two-story homes.
- It does not assess wall condition — rot repair, re-sheathing or adding insulation board behind new siding are separate scopes with separate materials.
FAQ
How do I measure my wall area?
For each wall: length × height. Add gable ends as triangles (½ × base × height). Sum all walls, then subtract doors and windows (about 15 ft² per window, 20 ft² per door if you do not want to measure each). Measure in full feet and round up — it is easier to return a carton than to match a dye lot later.
How much does siding cost?
Material commonly runs in the $200–$500 per square range depending on the product (2025–2026) — standard vinyl at the low end, fiber cement and engineered wood higher; installed cost commonly comes to two to three times the material figure. Quotes are given per square, so your calculator result is the number to compare them against.
Should I deduct every small window and vent?
Deduct doors and windows. Small vents, hose bibs and light fixtures are usually left in — the siding is cut around them anyway, and the tiny overage disappears into the waste allowance.
How much extra should I order for waste?
10% for simple rectangular walls, 12–15% when there are many openings, corners or gables. Keep any full leftover carton unopened for future repairs — color lots change and a patched wall in a mismatched lot shows.