Measured from the ground, counted to the bundle
How many squares is your roof, really?
60 free roofing calculators for homeowners, DIYers and roofers: shingles and flashing, pitch and rafters, metal, tile and flat roofs, gutters, attic ventilation and what a roof costs. Each one prints its formula, its sourced assumptions and the arithmetic next to the answer.
One 1,600 sq ft house at 6/12
- Roof area from the footprint
- 1,789 sq ft
- Architectural shingle bundles, 10% waste
- 60
- Synthetic underlayment, 10-square rolls
- 3
- Reroof of 2,000 sq ft, one layer off
- $12,200 to $21,900
A 40 × 40 ft footprint with no overhang; the cost uses 2025 survey ranges for architectural shingles. Change any of it in the calculators.
- 60calculators, each tested against worked examples
- 25guides on measuring, materials, gutters, ventilation and cost
- 0sign-ups or saved data: everything runs in your browser
- October 7, 2026when the coverage, code and cost figures were last checked
Calculators
Shingles & materials
Bundles, starter, ridge cap, nails, underlayment, ice barrier, drip edge and flashing from one roof measurement.
Shingle Calculator
Squares, bundles, ridge cap and nails for an asphalt shingle roof, from the roof area or the footprint and pitch.
Starter Strip Calculator
Bundles of starter shingles for the eaves and rakes from the edge lengths and the coverage per bundle.
Hip & Ridge Cap Calculator
Bundles and pieces of cap shingles for the ridge and every hip, at the exposure you choose.
Roofing Nails Calculator
Nails, pounds and boxes for a shingle roof from the squares, the nailing pattern and the nail length.
Roof Underlayment Calculator
Rolls of felt or synthetic underlayment and the cap nails to fasten them, with laps and waste counted.
Ice & Water Shield Calculator
Rolls of self-adhering membrane for the eaves, valleys and penetrations, with the courses the code distance needs.
Drip Edge Calculator
Pieces of drip edge for the eaves and rakes from the edge lengths, piece length and overlap, plus the nails.
Valley Flashing Calculator
Valley metal pieces and lining rolls for open, closed-cut and woven valleys from the valley lengths.
Step & Wall Flashing Calculator
Step flashing pieces for sidewalls and chimneys, kick-outs, counter flashing and whether a cricket is required.
Pitch & geometry
Pitch in any unit, true roof area from a footprint, rafter and hip lengths, truss counts, ridge height and ladder length.
Roof Pitch Calculator
Pitch from rise and run, degrees or percent, with the pitch factor, hip factor and what the slope means for roofing.
Roof Area Calculator
True roof surface area and squares from the building footprint, overhangs and pitch, with dormers and suggested waste.
Roof Pitch Factor Calculator
The pitch factor and hip factor for any pitch, with a table of the common pitches and the area or rafter length they give.
Rafter Length Calculator
Common rafter length from span or run and pitch, with ridge shortening, overhang, cut angles, birdsmouth and the board to buy.
Hip & Valley Rafter Calculator
Hip or valley rafter length, run, plumb and cheek cuts, drop and the jack rafter difference for a regular hip.
Truss Count Calculator
How many trusses a building needs at 12, 16, 19.2 or 24 in spacing, with gable-end trusses, lateral bracing and ties.
Gable Area Calculator
The triangle area of a gable end from its width and pitch or peak height, for siding and sheathing, with rake trim length.
Ridge Height Calculator
Rise and ridge height above the plate and above the floor or grade from span, pitch, wall height and rafter HAP, plus the fascia height.
Ladder Length Calculator
The extension ladder size for an eave height using the 4:1 angle rule and the 3 ft extension, with the base distance from the wall.
Metal roofing
Panels, standing seam, screws, trim and cut lists for corrugated, ribbed and standing-seam roofs, and what they cost.
Metal Roof Panel Calculator
Panels per side, panel length and total area for ribbed or corrugated metal roofing from the eave length, slope and coverage width.
Standing Seam Panel Calculator
Standing seam panels, clips and screws from the eave length, seam spacing, slope and clip spacing, for snap-lock, mechanical and nail-strip systems.
Metal Roof Screws Calculator
Panel screws, stitch screws and bags for an exposed-fastener metal roof from the squares or panels, the purlin spacing and the pattern.
Metal Roof Trim Calculator
Ridge cap, eave, rake, valley and wall trim pieces, closure strips, butyl tape, sealant and trim screws from the edge lengths.
Corrugated Shed Roof Calculator
Corrugated sheets, screws, ridge cap and foam closures for a gable or lean-to shed from its length, width and pitch.
Metal Panel Cut List
Panel counts and lengths for up to four roof sections with their own run and pitch, grouped into order lines, cut to length or from stock.
Metal Roof Cost Calculator
Installed cost range for an exposed-fastener, standing seam or metal shingle roof, with gauge, pitch, storeys, tear-off and region as separate lines.
Tile, slate & flat
Pieces per square for tile and slate, bundles of shakes, membrane rolls, rolled roofing and the battens under them.
Concrete & Clay Tile Calculator
Field tiles, pallets, ridge and rake tiles and the dead load for concrete, clay, S-tile and barrel roofs.
Slate Roof Calculator
Slates per square from slate size and headlap, total slates, copper nails and the weight of the roof.
Cedar Shake & Shingle Calculator
Bundles of cedar shakes or shingles at your exposure from the Cedar Shake and Shingle Bureau coverage rules, plus hip and ridge.
Flat Roof Membrane Calculator
Rolls of EPDM, TPO or PVC for a flat roof with turn-ups and seam laps, plus seam tape, adhesive and edge metal.
Rolled Roofing Calculator
Rolls of mineral-surfaced roll roofing for exposed-nail, concealed-nail or double-coverage application, with nails and cement.
Synthetic Slate & Composite Shingle Calculator
Pieces and bundles of synthetic slate or composite shake from piece width and exposure or the data sheet, with starter, ridge and weight.
Roof Battens Calculator
Batten rows, linear feet, pieces and fasteners for a tile or slate roof from the slope length and gauge, with optional counter-battens.
Gutters & drainage
Gutter length, downspout count and size from roof area and rainfall, hangers, slope, guards and rain barrels.
Gutter Length Calculator
Gutter length, sections, joints, corners, end caps, outlets and sealant from the eave runs of the house.
Downspout Count & Size Calculator
How many downspouts a gutter run needs and whether the gutter is big enough, from roof area, pitch and local rainfall intensity.
Gutter Hangers & Brackets Calculator
Hangers, fasteners and boxes for a gutter from its length, the number of runs and the spacing your climate needs.
Gutter Slope Calculator
The drop over a gutter run at 1/16 to 1/4 in per foot, the high and low end heights and the chalk-line marks between.
Roof Runoff & Rain Barrel Calculator
Gallons of runoff from a roof area per storm or per year, barrels to hold it and the rain that fills one.
Gutter Guard Calculator
Gutter guard pieces, packs and screws from the gutter length, runs, size and piece length.
Downspout Extensions & Splash Blocks Calculator
Downspout pipe, elbows, straps, extensions, splash blocks or buried drain to carry roof water away from the foundation.
Attic ventilation & insulation
Net free area by the 1:150 and 1:300 rules, ridge and soffit vents, box vents, attic fans, insulation depth and baffles.
Attic Ventilation Calculator
Net free vent area by the 1:150 or 1:300 rule, split between soffit intake and ridge or roof exhaust.
Ridge Vent Calculator
Feet of ridge vent, pieces and nails for the exhaust an attic needs, with the shortfall if the ridge is too short.
Soffit Vent Calculator
Rectangular, round or strip soffit vents, or vented soffit panel, to deliver an attic's intake net free area.
Roof Box Vent Calculator
How many box (low-profile) roof vents an attic needs for its exhaust and how to space them below the ridge.
Attic Insulation Calculator
Inches and bags of blown fiberglass, cellulose or batts to reach the Energy Star R-value for your climate zone.
Attic Fan Sizing Calculator
Powered attic fan CFM from attic volume and air changes or the 0.7 CFM rule, with the intake the fan needs.
Rafter Baffles Calculator
Rafter vent baffles for every vented bay, and whether one reaches past the insulation at your depth and pitch.
Cost, tear-off & hiring
Replacement cost per square by material, labor, tear-off weight and dumpster size, repairs, DIY vs pro and an estimate builder.
Roof Replacement Cost Calculator
Installed cost range for a new roof in any common material, with waste, pitch, storeys, tear-off, decking, region and permit as separate lines.
Roofing Labor Cost Calculator
Crew hours and labor cost for a roof from the squares, material, pitch, storeys and tear-off, at a billed rate you set.
Tear-Off Weight & Dumpster Calculator
The weight of an old roof by material and layers, the dumpster size and loads it needs and the disposal cost.
Roof Repair Cost Calculator
Cost range for common roof repairs (shingles, pipe boots, flashing, chimneys, valleys, skylights, leaks) with access and region.
Roofing Cost per Square Calculator
Turn a roofing quote into a price per square and per square foot, and see where it sits in the published range for its scope.
DIY vs Pro Roofing Calculator
What doing a roof yourself really saves against a quote once materials, rentals, disposal and your hours are counted, with the safety caveats.
Roofing Time Calculator
Worker-hours and days on site for a roof from squares, material, pitch, storeys, tear-off, crew size and a weather allowance.
Roofing Estimate Builder
Build a roofing estimate from materials, tax, labor, disposal and permit, with overhead and profit as margin or markup made explicit.
Lifespan, planning & solar
Lifespan and cost per year, when to replace, weight on the structure, solar fit, project scheduling and skylight sizing.
Roof Lifespan & Cost per Year Calculator
What a roof costs per year of life, with maintenance, compared with another material, from installed cost and expected life.
Roof Replacement Planner
The expected replacement window for a roof from its install date, material, climate, ventilation and the warning signs you can see.
Roof Weight Calculator
The dead load a roofing material puts on the structure, the change from the roof it replaces, and when an engineer should look.
Solar Panel Roof Fit Calculator
How many solar panels fit on a roof face after fire-code setbacks, in portrait or landscape, and the system size in kW.
Roofing Project Schedule
Finish date, book-by date and the order of work for a reroof from the start date, squares, material, crew and weather days.
Skylight Size Calculator
How much skylight glazing a room needs by daylighting rule and which standard sizes fit between your rafters.
No calculator matches that. Try "shingle", "pitch" or "gutter", or browse the full list and the guides.
How the estimates work
- Footprint and pitch become true roof areaThe building's length and width plus the overhangs, multiplied by the pitch factor √(1 + (rise ÷ 12)²), give the sloped area of every plane at once. No ladder needed.
- Coverage and waste become what you buyEach material's coverage comes from manufacturers' data, laps are subtracted, waste follows the roof's shape, and every count is rounded up to whole bundles, rolls, pieces and boxes.
- The arithmetic is on the pageEvery result has a breakdown table and a "Show the arithmetic" panel, so a surprising number can be traced to the input that caused it, and checked against a roofer's quote.
Most roofing calculators multiply a floor area by three and stop. These start from the roof's real geometry, count the edges as well as the field, apply the building code where it sets a quantity (ice barrier, underlayment laps, ventilation ratios), and price with dated survey ranges rather than a single number. They measure and count; they never certify a structure, and they never ask you to climb onto a roof.
Questions people ask first
- How many bundles of shingles are in a square?
- Three bundles cover one square (100 square feet) for three-tab and almost all architectural shingles. Heavy designer shingles are packed four or five to the square. Add 10 to 20 percent for waste before rounding up to whole bundles.
- How do I measure my roof without climbing on it?
- Measure the building at ground level, add the overhangs, and multiply the footprint by the pitch factor for your pitch, which you can read with a level held against a rake board. A 1,600 square foot footprint at 6/12 is about 1,789 square feet of roof.
- What is a 4/12 roof pitch in degrees?
- A 4/12 pitch rises 4 inches per foot of run: 18.4 degrees, a 33 percent slope, with a pitch factor of 1.054. It is the lowest pitch for standard single-layer underlayment under shingles.
- What does a new roof cost per square?
- Published 2025 cost surveys put installed architectural asphalt shingles at about $450 to $800 per square, metal at $800 to $2,500 and tile or slate at $1,000 to $4,000, plus $100 to $200 per square for each layer torn off.
- How many downspouts does a house need?
- At least one per gutter run and one per 30 to 40 feet of gutter, and enough capacity for the roof: a 2 × 3 inch downspout drains roughly 600 square feet and a 3 × 4 about 1,200 by the trade rule of thumb.
- How much attic ventilation do I need?
- The building code asks for 1 square foot of net free vent area per 150 square feet of attic floor, or 1 per 300 with balanced intake and exhaust. A 1,500 square foot attic needs 720 square inches under the 1:300 rule.
From the guides
Attic insulation R-values by climate zone, and how much to add
Most attics already have some insulation. Measure it, convert it to R-value, and the zone map tells you how much more to add.
Attic ventilation: the 1:150 rule and balancing intake and exhaust
An attic needs air moving from the eaves to the ridge. The code gives the amount; the balance between intake and exhaust decides whether it works.
Bundles per square and the waste nobody budgets for
The bundle count is easy; the waste is where orders come up short. Here is where every percent of waste goes and how to set it for your roof.
Cedar shakes and shingles: exposure, bundles and lifespan
A bundle of cedar does not cover a fixed area: it covers more at a longer exposure. The Bureau's rule makes the count simple once that is clear.
Downspouts: how many, where, and how far from the foundation
A gutter is only as good as the place its water ends up. Here is how to place downspouts so the water leaves the house and stays away.
Drip edge, step flashing and valleys: the pieces that stop leaks
Roofs rarely leak through shingles; they leak at edges, walls and valleys. Here is each flashing, what it does and how much of it a roof needs.
Built to be checked. Every calculator is tested against its own worked examples before it goes up. Coverage figures come from manufacturers' published data, code quantities from the International Residential Code, safety rules from OSHA and costs from dated 2025 surveys, all listed on the methodology page and last reviewed on October 7, 2026. The site is written by its publisher with AI assistance and human review. Found a figure that looks wrong? Tell us.
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