Calculators
Shingle and roofing material calculators
Bundles, starter, ridge cap, nails, underlayment, ice barrier, drip edge and flashing from one roof measurement.
Roofing is sold by the square, 100 square feet of roof surface, and bought in bundles, rolls and 10-foot sticks that never divide evenly into it. Every calculator in this group starts from the same two facts about your roof, its true area and the lengths of its edges, and turns them into whole things to put on the truck: bundles of shingles, rolls of underlayment, pieces of drip edge, boxes of nails.
The number that most often goes wrong is not the area but the waste. A plain gable roof loses about a tenth of its shingles to cuts at the rakes and the ridge; a hip roof loses more at every hip; a roof full of valleys and dormers can lose a fifth. The calculators set the allowance from the shape you pick and let you change it, and they round every quantity up to the unit you can actually buy.
9 calculators
Shingle Calculator
Squares, bundles, ridge cap and nails for an asphalt shingle roof, from the roof area or the footprint and pitch.
Starter Strip Calculator
Bundles of starter shingles for the eaves and rakes from the edge lengths and the coverage per bundle.
Hip & Ridge Cap Calculator
Bundles and pieces of cap shingles for the ridge and every hip, at the exposure you choose.
Roofing Nails Calculator
Nails, pounds and boxes for a shingle roof from the squares, the nailing pattern and the nail length.
Roof Underlayment Calculator
Rolls of felt or synthetic underlayment and the cap nails to fasten them, with laps and waste counted.
Ice & Water Shield Calculator
Rolls of self-adhering membrane for the eaves, valleys and penetrations, with the courses the code distance needs.
Drip Edge Calculator
Pieces of drip edge for the eaves and rakes from the edge lengths, piece length and overlap, plus the nails.
Valley Flashing Calculator
Valley metal pieces and lining rolls for open, closed-cut and woven valleys from the valley lengths.
Step & Wall Flashing Calculator
Step flashing pieces for sidewalls and chimneys, kick-outs, counter flashing and whether a cricket is required.
Guides for this topic
Bundles per square and the waste nobody budgets for
The bundle count is easy; the waste is where orders come up short. Here is where every percent of waste goes and how to set it for your roof.
Cedar shakes and shingles: exposure, bundles and lifespan
A bundle of cedar does not cover a fixed area: it covers more at a longer exposure. The Bureau's rule makes the count simple once that is clear.
Drip edge, step flashing and valleys: the pieces that stop leaks
Roofs rarely leak through shingles; they leak at edges, walls and valleys. Here is each flashing, what it does and how much of it a roof needs.
How to measure a roof from the ground (no ladder needed)
Everything a roofing order needs can be measured standing on the lawn. Here is the method, the one calculation that matters, and the checks that catch the usual mistakes.
Ice and water shield: where the code wants it and how much
One sentence of code decides how much membrane a roof needs, and the pitch decides how it reads on the deck. Here is the sentence and the arithmetic.
How to read a roofing estimate and compare two
Two roofing quotes for the same house can differ by thousands and both be honest. Lining them up item by item shows why.
Repair or replace: the signs, the maths and the timing
A leak does not always mean a new roof, and a dry ceiling does not mean the roof is fine. Age, signs and a simple sum decide it.
Roofing nails: count, length and nailing patterns
Most shingle blow-offs are nailing failures. The count is arithmetic; the placement and the depth are what hold a roof down.
Underlayment: felt vs synthetic, coverage and overlaps
The layer under the shingles is the roof's second line of defence. Choosing it is easy; counting it right means counting the laps.
Questions people ask
- How many bundles of shingles do I need for 20 squares?
- Standard three-tab and most architectural shingles are packed three bundles to the square, so 20 squares is 60 bundles before waste. With 10% waste for a simple gable roof that is 66 bundles; with 15% for a hip roof, 69. Heavier designer shingles are packed four or five to the square, so check the wrapper.
- How much starter strip does a roof need?
- Starter runs along every eave, and most installers also run it up the rakes. Add up those edge lengths, then divide by the coverage printed on the starter bundle, which is typically 100 to 120 linear feet. A 40 by 30 foot gable house with two 40-foot eaves and four 17-foot rakes needs about 148 feet, so two bundles.
- How many bundles of ridge cap for a roof?
- Add the ridge length to the length of every hip. A bundle of purpose-made cap covers roughly 20 to 35 linear feet depending on the product, and a bundle of three-tab shingles cut into caps covers about 33 feet at a 5-inch exposure. A 44-foot ridge with no hips therefore takes two bundles.
- How many nails per square of shingles?
- Manufacturers call for four nails per shingle in normal conditions and six in high-wind areas. Three-tab shingles run about 80 to the square, so 320 nails standard or 480 in high wind; architectural shingles run about 64 to the square, so roughly 256 or 384. A 50-pound box of 1¼-inch coil nails holds around 7,000.
- Where is ice and water shield required?
- The International Residential Code (R905.1.2) requires an ice barrier in areas with a history of ice forming along the eaves, running from the lowest edge of the roof to a point at least 24 inches inside the exterior wall line. With a 12-inch overhang and a 6-inch wall that is about 42 inches measured horizontally, which on most pitches means two courses of a 36-inch roll.
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