Roofing calculators start from one number that changes everything else on a roof: the pitch. A roof’s slope decides how much surface sits over the house, which roof coverings are allowed, how fast a crew can work and what safety gear the job needs. The tools on this page begin with that slope and the geometry behind it, and the roofing cost guides cover repairs, leaks, storm damage and cleaning, the work most homeowners price first.
Roofing tools
| Calculator | Best for | Main result |
|---|---|---|
| Roof Pitch Calculator | Finding the slope from rise and run, an angle or a pitch in 12 | Pitch, angle, percent grade, area multiplier, rafter length |
| Roofing Calculator | Ordering shingles for a gable or hip roof from the footprint and pitch | Roof area, squares, bundles with waste, rolls, ridge cap |
| Roof Square Footage Calculator | Finding the sloped roof area alone, with the full multiplier table | Roof square feet and squares |
| Roof Shingle Calculator | Turning a known roof area from a bid or report into an order | Bundles, rolls, ridge cap, installed shingle price |
| Roof Replacement Cost Calculator | Pricing a new roof with tear off by layer | Installed roofing, tear off, underlayment, total |
| Roof Cost Calculator | A quick budget from roof area, material and region | Total with one tear off layer and underlayment |
| Metal Roof Cost Calculator | Comparing standing seam and corrugated panels | Installed panel cost, optional tear off |
| Insulation Calculator | Blowing or laying insulation on the attic floor under the roof | Attic insulation quantity and price |
Why pitch comes first
A flat footprint and a sloped roof are not the same area. The roof surface equals the footprint times a multiplier that grows with the slope: 1.054 at 4/12, 1.118 at 6/12, 1.202 at 8/12 and 1.414 at 12/12. A house with a 1,500 square foot footprint and a 6/12 roof therefore has about 12 percent more roof than floor, before overhangs, dormers and valleys add their share.
That surface area drives the material order. Roofers count area in squares of 100 square feet, standard architectural shingles usually come 3 bundles to the square, and a typical synthetic underlayment roll in the site configuration covers 400 square feet. Getting the pitch wrong by a couple of inches in 12 can throw every one of those numbers off.
Measuring a roof safely
Pitch can be found from inside the house. In the attic, a level and a tape on the underside of a rafter give rise over a 12 inch run, and a phone angle reading on the rake trim gives degrees that the pitch calculator converts. Roofs steeper than 4 in 12 count as steep under federal OSHA rules, and work on them calls for fall protection.
Pitch and roofing materials
Model building codes set minimum slopes for each roof covering. Asphalt shingles need at least 2/12, with extra underlayment on the shallowest pitches, while slate needs 4/12 and standing seam metal can go much lower. Below the shingle limit, roofs move to membrane systems such as modified bitumen or single ply. The pitch calculator page lists these minimums with their sources.
Roof repair and cost guides
Most homeowners price a roof because something has gone wrong. The guide to signs of roof damage covers what to look for after a storm or in an aging roof. Repair pricing sits in the guide to roof leak repair costs and the emergency repair cost guide, the storm damage roof repair guide covers insurance claims and temporary protection, the flat roof repair guide covers low slope roofs, and the roof cleaning cost guide covers moss, algae and safe cleaning methods. Before any of that, the roof inspection cost guide prices a professional look at the roof, by walk on, drone or infrared scan.
Attic, insulation and the roof
The attic below a roof affects how long the roof lasts. Poor ventilation and missing insulation let warm, moist air reach the roof deck in winter, which feeds ice dams at the eaves and condensation on the sheathing. Baffles at the eaves keep soffit vents open when insulation goes down, and air sealing the ceiling below cuts the moisture reaching the attic. The insulation calculator sizes blown fiberglass and batts by R value for that attic floor.
When a roofer is needed
Roof work is among the most dangerous trades in construction, and falls from roofs are a leading cause of serious injury. Measuring from the ground or the attic, inspecting with binoculars and photographing damage are safe homeowner tasks. Replacing shingles, fixing flashing and anything on a steep or wet roof belongs with a roofer who carries fall protection and insurance. Roof replacements and structural changes usually need a permit.
Related tools and pages
The interior calculators cover drywall and insulation inside the house, including vaulted ceilings that follow the roof slope. The methodology page explains how every estimate on the site is built and dated.