How this siding calculator works
Siding is an area job measured in squares — 100 ft² each. Total the walls, take off the openings, add waste, and convert to the squares and boxes you order:
squares = net × (1 + waste) ÷ 100 · boxes = ⌈net × (1 + waste) ÷ box coverage⌉
At the defaults — 120 ft of wall at 9 ft, 120 ft² of openings, 10% waste — that is 960 ft² net, about 10.56 squares, or 6 boxes of 200 ft² siding, roughly $2,040; the full chain is in the worked example below.
Siding types, and the trim around them
“Siding” is a family of products that all install by the square but differ in price and handling. The common ones, plus the trim that never shows up in the square count:
- Vinyl: the volume material — sold in ~200 ft² boxes, cuts fast, lowest cost. The calculator’s default.
- Fiber cement (lap): heavy, durable, painted; sold by the plank but figured the same by the square.
- Engineered wood & aluminum: mid-priced lap options, same area math.
- Board & batten: vertical boards with battens over the seams — a different layout, priced on the board and batten calculator.
- Trim: J-channel, corner posts, starter and finish strips, house wrap — bought by the linear foot or roll, separate from the field squares.
What to measure, and what to leave out
The whole estimate is one number done carefully — net wall area. The rules that keep it honest:
- Wall run: add the length of every wall you’re siding — the full perimeter for a whole house.
- Gables: add each gable triangle — ½ × base × height — to the area; they get sided too.
- Openings: subtract doors and big windows; leave small windows in as free waste.
- Waste: 10% standard, 15% for lots of corners and angles.
- Stories: a two-story wall is just a taller height — measure to the top of the sided area.
Siding cost by type, and squares by wall area
Table 1 is the 2026 material range by siding type; Table 2 turns net wall area into squares and boxes at 10% waste and a 200 ft² box.
| Siding | $/square |
|---|---|
| Vinyl | $150–250 |
| Aluminum | $250–400 |
| Engineered wood | $200–350 |
| Fiber cement | $250–450 |
| Net wall | Squares | Boxes |
|---|---|---|
| 500 ft² | 5.50 | 3 |
| 1,000 ft² | 11.00 | 6 |
| 1,500 ft² | 16.50 | 9 |
| 2,000 ft² | 22.00 | 11 |
How to measure a house for siding
- Measure each wall’s length and height; total the runs, or the whole perimeter for a full re-side.
- Add the gables — half base times height for each triangle — to the wall area.
- Subtract the openings — total door and large window area — from the gross.
- Set 10% waste, or 15% on a cut-up house with lots of corners and angles.
- Read squares and boxes, then add trim, corners, starter and house wrap from the exclusions below.
Worked example: siding a 120 ft wall run
The default, worked line by line — 120 ft of wall at 9 ft high, 120 ft² of openings, 10% waste, 200 ft² boxes at $340:
net = 1,080 − 120 = 960 ft²
with waste = 960 × 1.10 = 1,056 ft² = 10.56 squares
boxes = ⌈1,056 ÷ 200⌉ = 6 · cost = 6 × $340 = $2,040
The rounding to whole boxes is where the spare comes from: six 200 ft² boxes cover 1,200 ft² against a 1,056 ft² need, so you finish with about a square in hand — which is exactly what you want, because a matched box put aside beats hunting the same dye lot after a storm.
What this siding estimate doesn’t include
The squares are the field siding; a finished wall needs the trim and weather layer around it:
- Trim and accessories. J-channel, corner posts, starter strip and finish trim — bought by the linear foot.
- House wrap. The weather-resistive barrier behind the siding, by the roll.
- Soffit and fascia. The overhang materials, figured separately by the linear foot.
- Fasteners and flashing. Nails, and flashing at windows, doors and transitions.
- Tear-off and repair. Removing old siding and fixing any sheathing behind it.
- Labor. Installation, most of a delivered siding cost.
Siding FAQ
How do I calculate how much siding I need?
Add up the wall area — total wall length × height — subtract the doors and windows, then add 10% for waste. The default 120 ft of wall at 9 ft is 1,080 ft² gross, 960 net after 120 ft² of openings, or about 10.56 squares (1,056 ft²) with waste — 6 boxes of 200 ft² vinyl, roughly $2,040 at the default price.
How many squares of siding do I need?
A square is 100 ft², the unit siding is measured and often priced in — so squares are simply your net wall area, plus waste, divided by 100. The 960 ft² default wall is 10.56 squares with 10% waste. Multiply squares by your price per square, or count boxes by their printed coverage, for the order.
How much siding for a 1500 square foot house?
Side the walls, not the floor: a single-story 30 × 50 ft house is a 160 ft perimeter, so at 9 ft walls that is 1,440 ft² gross. Take off about 150 ft² of openings and add waste and it is roughly 14.2 squares — 8 boxes of 200 ft² siding. Two-story homes of the same footprint need nearly double.
What is a square in siding?
One hundred square feet. Both siding and roofing are sold and quoted by the square, so a wall of 1,056 ft² is 10.56 squares. It keeps big numbers manageable and lets you compare products and bids on the same unit.
How much does vinyl siding cost?
Vinyl siding material runs about $150 to $250 per square in 2026 — the default 200 ft² box at $340 works out to $170 a square. Installed, siding commonly prices at $4 to $12 per square foot depending on material and trim, so labor and accessories are most of the delivered cost.
How much extra siding should I buy for waste?
10% is the standard allowance; go to 15% on a house with lots of corners, gables, or a complex layout, since every course that meets a corner or an angle leaves an offcut. Buy full boxes and keep a spare — dye lots vary, and matching a box a year later is a gamble.
Do I include gables and soffits in siding?
Add gable triangles to the wall area — each is ½ × base × height — since they get sided too. Soffit and fascia are separate products bought by the linear foot, and are not counted in the wall squares here. Measure the gables, add them to the run, and the calculator folds them into the total.
Sources and standards
The area math is geometry; the units and prices are industry practice:
- The square: 100 ft², the standard siding and roofing coverage unit.
- Manufacturer box coverage: vinyl cartons cover about 2 squares (200 ft²) — check the product.
- Waste practice: 10% typical, 15% for complex walls with many corners and gables.
- Editable prices: the 2026 per-square ranges are defaults; your supplier’s quote governs.
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