Roofing Calculators
Measure once, then let the numbers carry through. Each tool hands its result to the next step, from pitch to roof area to materials.
Roofing calculators
- Attic Ventilation Calculator
Net free vent area under the IRC 1/150 and 1/300 rules, with ridge, box and soffit vent counts.
- Gutter Size Calculator
Gutter size and downspout count from roof area, pitch and NOAA rainfall intensity for your state.
- Metal Roof Cost
Metal roof price by type and state, compared with shingles up front and per year of life.
- Roof Pitch Calculator
Pitch, angle, slope and multiplier from rise and run, degrees or x/12. Includes rafter length.
- Roof Replacement Cost
Low, typical and high cost for a new shingle roof, using roofer wages from your state.
- Roof Square Footage Calculator
Sloped roof area and roofing squares from house size and pitch, with waste and edge lengths.
- Shingle Calculator
Shingle bundles from roof area, with waste, starter strip, hip and ridge cap and nails.
- Underlayment Calculator
Rolls of synthetic or felt underlayment and ice barrier, with the code's low-slope and eave rules.
Where to start
Almost every roofing estimate depends on two numbers: the pitch of the roof and its footprint. Pitch tells you how much bigger the sloped surface is than the area the house covers, and whether a given material is even allowed on it. The footprint is the area you can measure from the ground, or take from a property survey, including the overhangs.
If you don’t know your pitch yet, start with the roof pitch calculator. It works from a level-and-tape measurement, an angle reading from a phone, or a pitch you already know, and it tells you the multiplier you’ll use for area.
How the numbers connect
- Pitch gives the slope factor (the pitch multiplier).
- Footprint × multiplier gives the sloped roof area, which roofers count in squares of 100 sq ft.
- Area plus waste gives material quantities: shingle bundles, underlayment rolls, drip edge and ridge cap.
- Quantities × local prices and labor gives a cost range.
Our calculators pass their results along this chain through the link at the bottom of each result, so you only type a measurement once.
A note on accuracy
These tools give planning numbers, not a contractor’s bid. Real roofs have valleys, dormers, skylights and chimneys that add waste and labor. Use the results to sanity-check quotes and to order materials with a sensible margin, and get at least two written bids from licensed, insured roofers before you sign anything.
Which roofing calculator do I need?
- “How steep is my roof?” Use the roof pitch calculator. It converts rise and run, an angle or an x/12 pitch into degrees, slope and the area multiplier, and tells you which materials the code allows at that pitch.
- “How big is my roof?” The roof square footage calculator turns house dimensions and pitch into sloped area and roofing squares, with waste and the edge lengths for drip edge and ridge cap.
- “How many bundles should I order?” The shingle calculator counts bundles with waste, plus starter strip, hip and ridge cap and nails.
- “How much underlayment and ice barrier?” The underlayment calculator gives rolls of synthetic or felt underlayment, with double layers on low slopes and ice barrier at the eaves.
- “Is my attic vented enough?” The attic ventilation calculator applies the IRC 1/150 and 1/300 rules and splits the vent area between ridge and soffit vents.
- “What size gutters do I need?” The gutter calculator checks 5 and 6 inch gutters against NOAA rainfall intensity for your state and tells you how many downspouts to install.
- “What will a new roof cost?” The roof replacement cost calculator prices an asphalt shingle roof with your state’s roofer wages, and the metal roof cost calculator compares metal with shingles up front and per year of service life.