How to Estimate a Roof Replacement From Your Measurements
From measured squares and edge footage to a priced, tiered bid: material lines, per-square labor, margin math and Good / Better / Best tiers, with a worked 28-square example.
To estimate a roof replacement from your measurements, turn the measured squares and line footage into a material list, add tear-off, labor, disposal and overhead, then divide the total cost by one minus your margin. Do that once per tier and you have a Good / Better / Best bid built on the same roof.
Quantities first, cost second, price last. Starting from last month's per-square number skips the part where this roof is different.
What you need from the measurement
Pull these before you open a price sheet:
- True squares. Slope-adjusted area, net of anything you're not roofing.
- Line footage by type. Eaves, rakes, ridges, hips and valleys, plus step and headwall flashing runs.
- Pitch. It moves labor and safety setup. No pitch yet? The free roof pitch finder gives you a starting number.
- Waste. Picked for this roof, not out of habit. Waste factor by roof type has the brackets.
- Layers, stories, penetrations. Layers and stories change tear-off; pipes and chimneys change flashing.
Turn the measurement into material lines
The coverage figures are rules of thumb; the wrapper and the manufacturer's instructions win.
| Line | Comes from | How to count it |
|---|---|---|
| Field shingles | True squares × (1 + waste) | Squares × bundles per square (often 3 for laminates; heavier lines run more) |
| Starter | Eaves, plus rakes if you start them | Footage ÷ lineal feet per bundle on the wrapper |
| Hip & ridge cap | Hip + ridge footage | Footage ÷ lineal feet per bundle on the wrapper |
| Underlayment | True squares × (1 + waste) | Area ÷ roll coverage (often 1,000 sq ft; check the roll) |
| Ice & water | Eave band, valleys, wall runs | Area plus laps and cuts ÷ roll coverage (often 200 sq ft; check the roll) |
| Drip edge | Eaves + rakes | Footage ÷ 10 ft sticks, allowing for laps |
| Valley metal | Valley footage, where you run metal | Footage ÷ sheet length, plus laps |
| Flashing | Step, headwall and sidewall runs | Step: one per course (run ÷ exposure). Headwall and sidewall: run ÷ piece length, plus laps |
| Vents and boots | Ridge footage, penetration count | Ridge vent footage ÷ section length; boots by count |
| Nails and sealant | Order squares | The nailing pattern in the manufacturer's instructions |
Decking stays off this list on purpose. Price rotten sheets per sheet in the contract, so a bad deck is a change order, not your loss.
Labor, tear-off and disposal
Price these per square, and watch which squares:
- Tear-off on measured squares. You remove what's on the roof; waste doesn't exist yet.
- Install on the basis you pay your crew. Paid on squares of material handled? Use order squares.
- Steep and high work. A per-square add for pitch above what your crew walks, and for second stories.
- Disposal. Containers from tear-off squares and your hauler's weight limit.
Overhead and margin
Put overhead into cost: your yearly overhead spread over the jobs you expect to run. Then price on margin:
Price = total cost ÷ (1 − margin)
Markup is not margin. $12,080 of cost × 1.30 = $15,704, a 23% margin (3,624 ÷ 15,704). A real 30% margin is 12,080 ÷ 0.70 = $17,257. That's $1,553 short on one roof.
Good / Better / Best: what changes between tiers
Same roof, same squares, same tear-off. What moves:
| Tier | Shingle | Underlayment and ice & water | Warranty |
|---|---|---|---|
| Good | Standard laminate | Synthetic; ice & water at eaves and valleys | Base manufacturer and workmanship terms |
| Better | Next line up | Adds ice & water at walls and penetrations | Enhanced manufacturer warranty, where you qualify |
| Best | Premium line | Fuller ice & water coverage | Your longest manufacturer and workmanship terms |
Gutters and skylights ride on any tier as add-ons. Build each tier from its own material quote; don't mark Good up a percentage and call it Best.
Worked example: 28 squares, 6/12, gable and hip
Assumptions: 28 true squares at 6/12, one layer, one story, 10% waste; 160 lf eaves, 60 lf rakes, 45 lf ridge, 60 lf hips, 30 lf valley. Coverage: 3 bundles a square, 105 lf per starter bundle, 25 lf per cap bundle, 1,000 sq ft underlayment rolls, 200 sq ft ice & water rolls. Check your wrappers.
- Order squares: 28 × 1.10 = 30.8
- Shingles: 30.8 × 3 = 92.4 → 93 bundles
- Starter: 160 + 60 = 220 lf ÷ 105 = 2.1 → 3 bundles
- Hip & ridge: 45 + 60 = 105 lf ÷ 25 = 4.2 → 5 bundles
- Underlayment: 3,080 sq ft ÷ 1,000 = 3.08 → 4 rolls
- Ice & water: one 3 ft course on 160 lf of eave = 480 sq ft, plus 3 ft × 30 lf of valley = 90 sq ft; 570 × 1.10 for laps and cuts = 627; 627 ÷ 200 = 3.1 → 4 rolls (run more where your code or the manufacturer calls for it)
- Drip edge: 220 lf ÷ 9.83 ft per stick after a 2-inch lap = 22.4 → 23, plus a spare → 24 sticks
The dollar figures below are placeholders to show the arithmetic, not market rates.
- Tear-off: 28 sq × $50 = $1,400
- Install: 30.8 sq × $100 = $3,080
- Disposal: $600
- Overhead share: $1,000
That's $6,080 on every tier. Materials per tier, each from its own list and quote: Good $5,200, Better $6,000, Best $7,400.
| Tier | Total cost | Price at 30% margin | Rate per order square |
|---|---|---|---|
| Good | $11,280 | $16,114 | $524 |
| Better | $12,080 | $17,257 | $561 |
| Best | $13,480 | $19,257 | $626 |
Price = cost ÷ 0.70. Rate = price ÷ 30.8 order squares, rounded up.
Where RoofStruct fits
The Cost & Takeoff worksheet is free on every plan. It builds the cost side from a scaled measurement of a shingle roof: tear-off and disposal, area materials, linear accessories, labor and a decking rot allowance (zero its quantity if your contract prices sheets). Quantities recompute from the measurement and its waste setting; unit costs are defaults you overwrite with your own. It shows Total Job Cost, Net Profit at your target margin, and break-even per measured square.
On Pro, Good / Better / Best estimates price each tier as a rate per square × waste-adjusted true squares, plus add-ons, with optional tax, discount and deposit. Each tier carries its own feature list and warranty line, and the homeowner signs by typing their name. Tier rates start from your default pricing and are editable on each estimate; nothing carries over from the worksheet. Add overhead to the worksheet as a custom line, then convert: rate = Total Job Cost ÷ (1 − margin) ÷ the estimate's waste-adjusted squares, at the waste you priced.
Haven't measured yet? Measure your first roof walks through it.
Where you trip
- Mixing square bases. A $561 rate built on 30.8 order squares, multiplied by 28 measured squares, bills $15,708: a 23% margin on $12,080 of cost.
- Upgrading only the shingle. Enhanced warranties often require the manufacturer's accessories, such as starter and cap. Check the terms; price them into Better and Best.
FAQ
Should I estimate on true squares or plan squares?
True squares. Shingles, underlayment and labor follow the slope area. On a 6/12 the slope factor is 1.118, so 25 plan squares are 25 × 1.118 = 27.95 true squares.
Should I price tiers per square or per job?
Build cost per job, then convert to a rate on the squares your estimate multiplies. The rate survives a measurement change; the homeowner still sees a job total.
How do I handle a second layer?
Add an extra-layer tear-off line on the squares that carry it, and count the extra weight in disposal.
Close
Quantities from the roof, costs from your supplier and crew, price from your margin. Skip a step and the bid is a guess.