From footprint to rooftop
Roofing Shingle Calculator
How many shingle bundles do you need? Plan roof sections from horizontal footprints or measured roof surfaces, then budget for shingles, starter, ridge caps, and supplies.
How to calculate roof shingles without applying pitch twice
- Choose the measurement basis for each section. Horizontal footprint means the roof's plan-view projection, including overhangs. Measured roof surface means the actual sloped area.
- Enter area and exclusions. Use square feet or square meters consistently. Excluded areas must use the same basis as the section area. Include each non-overlapping roof section only once.
- Apply pitch only to footprints. Enter rise per 12 units of horizontal run for each footprint section. Measured roof surfaces bypass pitch entirely.
- Set product coverage and allowance. Enter bundles per roofing square or coverage per bundle from the label. Set a shingle allowance for each section.
- Complete the supply budget. Add starter and cap lengths, enable supplies, enter package coverage and prices, and add sales tax. Print or export the shopping list.
A rectangular footprint area is length × width measured horizontally. A rectangular measured roof face is its actual along-slope length × width. A whole-building footprint can represent a simple roof when its sections have the same pitch; separate areas with different pitches instead of applying one pitch to the entire building.
This is a materials estimator, not an installation or product-eligibility assessment. Choose a roofing system appropriate for the slope, climate, substrate, and manufacturer instructions.
Roof pitch, roofing squares, and shingle bundle formulas
Footprint method: roof area = (entered area − exclusions) × pitch factor
Measured surface method: roof area = entered area − exclusions
Order area = roof area × (1 + shingle allowance ÷ 100)
Roofing squares = combined order area in ft² ÷ 100
Bundles = round up(combined order area ÷ bundle coverage)
One roofing square is 100 square feet. If your label specifies bundles per square, coverage per bundle is 100 divided by that number. Sections using the same product are combined before rounding to whole bundles. The calculator uses unrounded values for the order.
Underlayment packages use net roof surface area and a separate supply allowance. Starter and ridge / hip cap packages use entered linear lengths and their own coverage. Field shingles, starter, and caps are separate order lines. Main shingle waste is not automatically applied to supplies.
Example: 1,000 square feet of footprint at 6:12 pitch
A horizontal footprint of 1,000 ft² at 6:12 pitch has a slope factor of approximately 1.118, giving about 1,118.03 ft² of roof surface. A 10% shingle allowance brings the order area to approximately 1,229.84 ft², or 12.30 roofing squares.
At an illustrative $38 per bundle: 37 × $38 = $1,406
This is the field-shingle subtotal before starter, caps, underlayment, other supplies, and tax. If 1,000 ft² is already a measured sloped roof area, choose measured roof surface instead: with the same allowance and coverage, the order is 33 bundles. Applying pitch again would overstate that measured surface.
Roofing shingle calculator FAQs
Should I enter building footprint or actual roof area?
Either can be used when you select the matching method. Enter the horizontal roof projection for footprint mode, including overhangs, then apply the section's pitch. Enter actual sloped area for measured roof surface mode; no pitch adjustment is made.
How many bundles make a roofing square?
The starting example is three bundles per 100-square-foot square, but products differ. Enter the number or coverage on your selected shingle label. The order is rounded up to full bundles after combining roof sections.
How much shingle waste should I allow?
The default 10% is an editable assumption. Roof geometry, cutting patterns, hips, valleys, dormers, and spare stock affect requirements. Enter an allowance for each section based on your layout and supplier guidance.
Are starter shingles and ridge caps included?
Enable them in supplies, enter the corresponding edge lengths, and replace the example package coverage with the effective coverage of your product. They are ordered separately from field shingles. Lengths are not inferred from area.
Does underlayment coverage account for overlaps?
Enter effective installed coverage after the overlaps required for your product and application, then add your chosen allowance. The calculator does not derive overlaps or code requirements. Partial-area membranes, flashing, and fasteners can be entered as manual package quantities.
What is included in the roofing cost and weight?
The budget includes field bundles, enabled supply quantities, and entered sales tax. Prices start at zero. Labor, delivery, tear-off, disposal, and unentered materials are excluded. Weight covers field-shingle contents only, excluding supplies and packaging.
Can I save or export a roof estimate?
The latest valid project saves in this browser when local storage is available. You can export a section and shopping-list CSV or print a summary to save as PDF. Reset starts fresh. All calculations and project data stay on your device.
