Roof shingle calculator

Enter the area your roof covers on the ground and its pitch. The pitch multiplier is the step almost every other calculator skips — a 6/12 roof has 12% more surface than its footprint, which is four extra bundles on an average house.

Roof area The area the roof covers seen from above, including overhangs. If you have already measured the sloped surface, set pitch to "already the sloped area". Roof pitch (rise per 12 in of run) Extra for waste % 10% on a simple gable. 15% once you have hips, valleys, dormers or a cut-up roof. Bundles per square Printed on the wrapper. Anything heavier than a standard laminate ships in more, lighter bundles. Total length of eaves and rakes to be starter-coursed Eaves at minimum. Add the rakes if you are starting the gable edges too. Total length of ridges and hips Starter strip coverage per bundle ft CertainTeed SwiftStart is 116-1/4 lineal ft per bundle. Check your product — this one varies a lot. Hip and ridge cap coverage per bundle ft CertainTeed Shadow Ridge is 30 lineal ft per bundle. Read the wrapper on yours.

Bundles of shingles 37 bundles

Actual roof surface 1,118 sq ft Pitch applied, before waste.

Roof size in squares 11.18 squares

Starter strip bundles 1 bundles

Hip and ridge cap bundles 2 bundles

Pitch is the number everyone drops

A roof is a slope, and a slope is longer than the ground under it. For a roof rising r inches per 12 in of run, the surface is

multiplier = √(1 + (r ÷ 12)²)

which gives 1.031 at 3/12, 1.054 at 4/12, 1.118 at 6/12, 1.202 at 8/12 and 1.414 at 12/12. A 6/12 roof — the most common pitch on an American house — therefore has 11.8% more surface than its footprint. On a 1,000 sq ft footprint that is 118 sq ft, or between three and four extra bundles. A calculator that takes your footprint and treats it as roof area will send you back to the supplier mid-tear-off, matching a dye lot you may no longer be able to get.

To measure pitch without climbing: hold a 2 ft level against a rafter or the gable trim, mark 12 in along it from the point of contact, and measure straight down from that mark to the roof. That drop in inches is the rise.

Squares, and why we do not round to them

One square = 100 sq ft, and standard 3-tab and architectural shingles pack three bundles to the square — CertainTeed's Landmark data sheet lists 3 bundles and 65 shingles per square, at a 5-5/8 in exposure. Heavier laminates go four or five bundles to the square because a bundle has to stay liftable.

Bundles are sold one at a time, so the arithmetic is:

bundles = ⌈ footprint × pitch multiplier × (1 + waste) ÷ 100 × bundles per square ⌉

A 1,000 sq ft footprint at 6/12 with 10% waste is 1,229.8 sq ft, which is 12.30 squares, which is 37 bundles. Round up to 13 whole squares first and you get 39 — two bundles of dead money and an effective waste factor of 15% rather than the 10% you asked for. Whole-square buying is a real yard habit, but it is a purchasing decision, not arithmetic, and you should make it knowingly.

One footnote: three bundles of Landmark cover 98.4 sq ft, not a full 100. That 1.6% shortfall sits comfortably inside a 10% waste factor, which is part of why the waste factor exists.

Starter and cap are separate purchases

Field shingles do not include the two courses that actually keep the roof on.

Starter strip runs the eaves, and the rakes if you want sealed gable edges. It is priced by lineal foot; CertainTeed SwiftStart covers 116-1/4 lineal ft per bundle.
Hip and ridge cap runs every ridge and every hip. Shadow Ridge covers 30 lineal ft per bundle, so caps go quickly on a hip roof.

Cutting three-tabs into your own caps is still done, but it voids most manufacturer system warranties, and it does not work at all with architectural shingles.

Common cases

Questions people ask

How many bundles of shingles in a square?

Three, for 3-tab and most architectural shingles. A square is 100 sq ft of roof, and the three bundles are sized so one person can carry one. Heavy laminate and designer profiles come four or five bundles to the square instead.

How many bundles of shingles for a 1000 sq ft roof?

If 1,000 sq ft is the actual sloped surface, 33 bundles with 10% waste. If it is the house footprint and the roof is 6/12, the real surface is 1,118 sq ft and you need 37 bundles. The two questions get very different answers, so be clear which one you are asking.

How do I measure my roof pitch from the ground?

From inside the attic or against the gable trim, hold a level horizontal, mark 12 in along it, and measure the vertical drop from that mark to the underside of the roof. A 6 in drop is 6/12. You do not need to get on the roof.

How much waste should I allow for shingles?

Ten percent for a plain gable roof with straight runs. Fifteen percent once you have hips, valleys, dormers or a chopped-up roof plan, because every valley cut throws away part of a shingle. Steeper roofs also waste more at the ridge.

Do I need starter strip and ridge cap on top of the bundles?

Yes. Both are separate products sold by the lineal foot, and neither is included in your square count. Skipping starter strip is a common cause of blow-off along the eaves, and most manufacturers require both for a system warranty.

Last reviewed 2026-07-30