Shingle calculator — bundles, courses and pallets

Three, for both three-tab and standard architectural shingles, and that is the figure to plan with. The exceptions are worth knowing: heavyweight designer laminates that imitate slate or shake bury more of each course and come four to the square, occasionally five, and a few specialty products state their coverage per bundle in square feet without ever naming a bundle count. Whatever the wrapper says beats the rule, which is why the bundles-per-square field is editable rather than fixed.

Only across a break in the roof, never within a plane. They differ in thickness, in exposure and in where the nail line falls, so a course of one laid into a course of the other leaves a step you can see from the driveway and a fastener that lands in the wrong part of the shingle below. Where a garage or an addition is genuinely a separate roof with its own ridge, mixing is a cosmetic decision rather than a technical one — and it still shows.

From three-tab, yes: cut the strip at the two tab slots and one shingle gives three caps, so a 26-piece bundle covers about 32 ft of ridge at a 5 in exposure. From a laminate, no. The two plies of an architectural shingle are bonded across the strip, and a cap cut from one splits along that bond as soon as it is bent over a ridge — usually not on the day it is fitted, which is what makes it an expensive shortcut. Hip-and-ridge product for laminate roofs is not an upsell, it is the only version that survives.

Exposure is the height of each course left showing to the weather once the course above it is laid, and it is the only part of a shingle doing any covering. The rest is headlap, buried under the next row. Reduce the exposure by half an inch and every course covers less roof, so more pieces are needed to reach the same square — which is why laying tighter than the printed reveal to make a roof look denser quietly puts the job over budget and, worse, moves the nail line into the wrong zone on the shingle underneath.

Do not cut it that narrow. Take a fraction of an inch off several courses on the way up so the last one lands at a usable height, which is why roofers snap their chalk lines from a course count rather than measuring up from the eave each time. The course panel shows what the top course is currently reduced to so the decision gets made at the bottom of the roof rather than discovered at the top of it. A sliver course has almost no nail room above the sealant line and is the first thing to lift in a wind.

Spread them, do not stack them. A bundle is 55 to 80 lb, so a pallet's worth landed on one spot puts well over half a ton on a couple of rafters — laid flat over the ridge in ones and twos, the same weight is nothing. The other reason to spread them is temperature: bundles stacked in a pile in July soften in the middle and take a set, and a shingle that has curled to the shape of the bundle above it never quite lies flat again.

Keep three or four and return the rest. Asphalt shingles are made in batches and the granule blend drifts between production runs, so a repair made from a bundle out of the original lot disappears where one bought two years later reads as a patch in low sun. Store them flat and out of the sun, on their side or laid over a joist rather than folded over anything, and label them with the roof date — the color name on the wrapper stops meaning much once a manufacturer revises the blend.