Explorer eight top-notch online tools for pitch, area, materials, cost, ventilation, and gutters calculations. No email capture, no satellite guesswork, no address required — just the math, in feet or meters, with a plain-English guide on every page.
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All 8 roofing calculators
Roof Pitch Calculator
Pitch ratio, angle in degrees, slope %, pitch multiplier, rafter length, ridge height, and walkability — from rise and run.
Open calculator MeasureRoofing Area Calculator
True sloped roof area for gable, hip, shed, gambrel, and pyramid roofs — from footprint and pitch, including overhangs.
Open calculator MeasureSlope Calculator
Slope, grade %, ratio, and angle — for roofs, ramps, driveways, and drainage paths.
Open calculator MaterialsShingle Calculator
Squares, bundles, underlayment, ridge cap, starter strip, drip edge, nails, and cost — for any asphalt shingle type.
Open calculator MaterialsMetal Roof Calculator
Panel count by length, standing seam clips or exposed screws, trim, underlayment, and honest 50-year cost comparison.
Typical: $10–$14 per sq ft installed Open calculator EstimateRoof Cost Calculator
Seven-line itemized estimate with cost per square, per square foot, and per year of life — plus a 12-point quote audit.
Typical: $9k–$18k asphalt · $20k–$30k metal Open calculator VentilateRoof Ventilation Calculator
Required net free area at 1:150 or 1:300, balanced intake and exhaust targets, and exact vent counts by type.
Open calculator DrainGutter Calculator
Recommended gutter size from effective area, downspout count and spacing, and installed cost — no lead form.
Open calculatorWhich roofing calculator do I need?
Roofing projects move through five stages: measure, calculate materials, estimate cost, ventilate, and drain. Pick the stage you are at — most people only need two or three of these for a single project.
Roofing calculator comparison
The fastest way to choose is to match the question you are trying to answer. Here is what each tool answers, what you need to bring, and what it returns.
| Tool | Stage | Answers | You bring | You get |
|---|---|---|---|---|
| Roof Pitch | Measure | How steep is the roof? | Rise and run | X:12 ratio, angle, multiplier, walkability |
| Roofing Area | Measure | How big is the sloped surface? | Footprint + pitch + roof shape | True sloped area in sq ft or m² |
| Slope | Measure | How sloped is any surface? | Rise and run or angle | Slope %, grade, ratio, degrees |
| Shingle | Materials | How many shingles to order? | Area or footprint + pitch | Squares, bundles, underlayment, accessories |
| Metal Roof | Materials | How many metal panels? | Area + panel type + pitch | Panel count, clips, trim, installed cost |
| Roof Cost | Estimate | What will the project cost? | Area + material + tear-off + region | Seven-line itemized estimate + per-year cost |
| Ventilation | Ventilate | How much attic venting? | Attic floor area + ratio + vent type | Net free area, intake/exhaust split, vent count |
| Gutter | Drain | What gutter size and spacing? | Roof area + pitch + rainfall | Gutter size, downspout count, installed cost |
Roofing conventions by country
Roofing measurements are not universal — the same roof can be expressed three different ways depending on where the drawings, contractor, or calculator came from. If you are comparing a US quote to a UK one, or reading a spec sheet from a manufacturer in another market, these are the differences that catch people out.
Pitch notation
- US / Canada: X:12 ratio — a 6/12 roof rises 6″ for every 12″ of run
- UK / Europe / Australia: degrees — a 6/12 roof is 26.6°
- Some contractors and drainage specs: slope percentage — a 6/12 roof is 50%
- Convert any of the three in the Roof Pitch Calculator.
Area units
- US: 1 roofing square = 100 sq ft, sold in squares and bundles (3 bundles per square for standard shingles)
- UK / Europe / Australia: measured directly in square metres — there is no "square" equivalent
- 1 sq m ≈ 10.76 sq ft, so a 20-square US roof is about 186 m²
Minimum pitch for shingles
- US (IRC R905): 2/12 with double underlayment, 4/12 standard
- UK (BS 5534): 15° for interlocking tiles, 20° for plain tiles — higher than US minimums
- Europe: varies by material and standard; most specify 15–22° minimum
- Below those thresholds, use a membrane, not shingles.
Material naming
- US "architectural shingle" ≈ UK "interlocking tile" in function (layered profile, 25–50 year life)
- US "3-tab shingle" ≈ UK "plain tile" in function (flat, 20–25 year life)
- Standing seam metal is called "standing seam" almost universally; sometimes "click-lock" or "snap-lock" in UK depending on profile
Rafter and ridge notation
- US: rafter length measured as the slope length from wall to ridge, in feet-inches
- UK / Europe: rafter length often given in metres, and "rafter run" sometimes refers to horizontal run rather than slope length
- Always confirm which measurement a drawing means before ordering.
Gutter sizing
- US (SMACNA): 5″ K-style handles about 1,500 sq ft effective area at 4 in/hr rainfall
- UK / Europe (BS EN 12056): gutters are sized by flow rate in litres/second, not by effective area
- If you are quoting a European product for a US roof, convert with the rainfall in in/hr or mm/hr at your specific site.
About these calculators
Every calculator on this hub is a single-purpose tool that answers one roofing question and hands you the number you need for the next step. They share the same design, the same unit flexibility (feet or meters), and the same refusal to ask for an email — no lead forms, no address capture, no satellite imagery that gets complex roofs wrong.
The formulas follow published industry standards: pitch and area use the rise/run triangle and pitch multiplier; shingles use 3 bundles per square and the pitch multiplier for footprint conversion; metal uses linear feet of panel divided by panel length; cost uses the seven-line estimating model with material/labor split of roughly 40/60; ventilation uses IRC R806.2 at 1:150 or 1:300; and gutters use SMACNA effective area sizing with pitch and rainfall factors.
None of these tools replaces a local code review, a site-specific engineered design, or a licensed contractor's on-site assessment. They are estimating tools — the kind a professional would use at the desk before walking the property. If a calculator disagrees with a contractor's quote, ask the contractor why. There is usually a good reason (decking rot, code upgrade, complex geometry) that no calculator can see.
Frequently asked questions
What roofing calculators do you have?
Which roofing calculator should I use first?
Are these calculators really free with no lead form?
Do the calculators work in metric?
Why does the calculator disagree with my contractor's quote?
Why do satellite roof calculators disagree with each other?
Can I use these on a phone?
More from Builders Measures
Adjacent tools that often get used alongside a roofing project — plus the full fence calculator hub for the yard around the house.
Stair Calculator
Risers, tread, total run, step count, and code defaults — for exterior stairs to a roof deck, garage, or side entry.
Open calculator AdjacentLumber & Board Foot Calculator
Board feet, linear feet, pieces to buy with waste, and cost — for rafters, purlins, fascia, and any wood framing that supports a roof.
Open calculatorLooking for fence area, cost, post spacing, or paint calculators? See the fence calculators hub — 9 tools and 7 in-depth guides.