Modified Bitumen Calculator

Sheet rolls, adhesive, and cap sheet for mod-bit roofing.

Roof Footprint (sqft)

Pitch (rise per 12 in)

Roof Perimeter (LF)

Roof Penetrations

Waste Factor (%)

Tab to move between fields

Actual Roof Area (sqft)

3,003

Base Sheet Rolls38

Cap Sheet Rolls38

Total Rolls76

Primer (gallons)14

Flashing Rolls7

Mastic/Sealant Tubes12

Est. Material Cost ($)$4,155.00

Roof Squares33.03

Penetration Flashing Sqft16%

How to Use This Calculator

Enter roof footprint (sqft), pitch, perimeter (LF), and number of penetrations.
Set waste factor (%) (typically 10-15% for modified bitumen).
Review calculated roof area, base sheet rolls, cap sheet rolls, and flashings.
Add primer, adhesive, and flashing quantities for penetrations and perimeter terminations.
Torch-applied modified bitumen requires certified installers -- verify contractor qualifications.

How the result changes with Roof Footprint (sqft)

Roof Footprint (sqft): Horizontal projected area of the roof in square feet.
Pitch (rise per 12 in): Roof slope as inches of rise per 12 inches of run. Mod-bit is typically low-slope (0.25-3).
Roof Perimeter (LF): Total perimeter of the roof in linear feet for edge flashing.
Roof Penetrations: Number of pipes, vents, HVAC units, and other roof penetrations.
Waste Factor (%): Extra material for laps, cuts, and waste. 10-15% is standard.

Actual Roof Area (sqft): True roof surface area accounting for pitch.
Base Sheet Rolls: Number of base sheet rolls (mechanically fastened or self-adhered).
Cap Sheet Rolls: Number of modified bitumen cap sheet rolls.
Total Rolls: Combined base and cap sheet rolls.
Primer (gallons): Gallons of asphalt primer for substrate preparation.
Flashing Rolls: 33 ft rolls of flashing membrane for perimeter and edges.
Mastic/Sealant Tubes: Tubes of mastic sealant for edges and penetrations.
Est. Material Cost ($): Approximate material cost (labor not included).

Identify Input Parameters
4 parameters
Roof Footprint (sqft) = 3000, Pitch (rise per 12 in) = 0.5, Roof Perimeter (LF) = 220, Roof Penetrations = 4 = 5 input(s) provided
Calculate Actual Roof Area
Actual Roof Area = footprintSqft * pitchFactor
3003 = 3003
Calculate Base Sheet Rolls
Base Sheet Rolls
38 = 38
Calculate Cap Sheet Rolls
Cap Sheet Rolls
38 = 38