All roofing calculators
Twelve tools covering pitch, area, framing, materials, cost and load. Every result shows its working and links to the formula it came from.
Pitch & Slope
Pitch tools convert between the three ways a roof slope gets written down: the rise-over-run ratio used on US framing plans, the angle in degrees used almost everywhere else, and the percentage grade used in drainage design. Every tool here works from the same arctangent relationship, so results agree across the set.
- Roof Pitch CalculatorFree roof pitch calculator. Enter rise and run to get pitch as X:12, the angle in degrees, slope percentage and the pitch multiplier, with a live diagram.
- Roof Slope CalculatorCalculate roof slope from rise and run. Get slope as a percentage, an angle in degrees and an X:12 ratio, with drainage guidance and a live diagram.
- Roof Pitch to Angle ConverterConvert roof pitch to degrees and back. Enter any X:12 pitch or any angle to get the exact conversion, slope percentage, multiplier and a full reference table.
Area & Measurement
A roof is always larger than the building underneath it. These tools apply the correct pitch multiplier to a measured footprint so you order materials for the real surface, not the plan view.
- Roof Area CalculatorCalculate true sloped roof area from your building footprint and pitch. Get square feet, square metres, roofing squares and a waste-adjusted order quantity.
- Roof Square Footage CalculatorWork out roof square footage from ridge length, rafter length and pitch. Converts to roofing squares, square metres and a bundle count for shingles.
- Sloped Roof Area CalculatorConvert building footprint area to true sloped roof area using the pitch multiplier. Get roofing squares, square metres, and a waste-adjusted order quantity.
Framing & Structure
Framing tools work in the same right triangle: run, rise and rafter. Give any two and the rest follow. Results include the plumb and seat cut angles you need at the saw.
- Rafter Length CalculatorCalculate common rafter length from span and pitch. Get the line length, overall length with overhang, plumb and seat cut angles, and a span reference table.
- Rafter Angle CalculatorCalculate rafter cut angles, birdsmouth size and speed square settings from span and pitch. Get plumb cut, seat cut, rafter length and a cut diagram.
- Roof Truss CalculatorCalculate how many roof trusses you need, plus peak height, top chord length and bottom chord length from your span, pitch and spacing.
- Purlin CalculatorWork out purlin spacing, total linear feet and number of purlins for a metal roof. Includes span, pitch, overhang and common spacing presets.
- Hip Rafter CalculatorCalculate hip rafter length, plumb and side cut angles, and the number of jack rafters for a hip roof from span, pitch and overhang.
Materials & Quantities
Material tools take a roof area and turn it into orderable units — bundles, squares, panels, rolls and sheets — with a waste allowance you control.
- Roof Shingle CalculatorWork out how many shingle bundles and squares your roof needs. Includes waste allowance, starter strip, ridge cap and nail quantities for asphalt shingles.
- Metal Roof CalculatorCalculate metal roofing panels, panel length, screws and trim from your roof dimensions and pitch. Works for standing seam and exposed-fastener panels.
- Roof Tile CalculatorCalculate how many roof tiles, bundles and underlayment rolls you need for clay, concrete or Spanish tile roofs from footprint, pitch and waste.
- Underlayment CalculatorCalculate how many rolls of roofing underlayment you need for any roof area. Supports #15 felt, synthetic and ice-and-water shield coverage widths.
- Roofing Nails CalculatorEstimate roofing nails or screws by weight and count for shingles, metal panels and underlayment. Supports 4-nail and 6-nail patterns.
- Roof Sheathing CalculatorCalculate how many plywood or OSB roof sheathing sheets you need from roof area, sheet size and waste. Supports 4×8 and metric panels.
Cost & Estimating
Cost tools separate materials, labour, tear-off and disposal so you can see what actually drives a quote. Change any rate to match a real bid you have in hand.
Load, Drainage & Performance
Load and drainage tools apply published code methods — ASCE 7 for snow and wind, IPC for drainage — to your roof geometry. They size for a first-pass check, not a stamped design.
- Snow Load CalculatorCalculate flat and sloped roof snow load from ground snow load using the ASCE 7 method, including exposure, thermal and importance factors and total roof load.
- Gutter Slope CalculatorCalculate the correct gutter slope and total drop over any run. Get fall per foot, downspout count and the high and low end heights for a level line.
- Gutter Size CalculatorSize gutters and downspouts from roof area, pitch and local rainfall intensity. Get recommended gutter profile, downspout count and capacity check.
- Ridge Vent CalculatorCalculate ridge vent length and net free vent area for balanced attic ventilation. Matches intake vent area and gives code-compliant NFVA guidance.