Roof Shingle Calculator – Estimating The Requirement Of Shingles

A roof shingle calculator will be of invaluable help to homeowners to make a correct estimate about the number of roofing shingles needed for a job or a re-roofing project. Give yourself lot of time to assess and making the required math to know the number and quantity of shingles, the felt paper, under-layment, flashing, nails, vents, turbines, ridge caps and other materials needed to complete a roofing project.

When you do a thorough job and make your calculations as accurate as possible you will be able to order all the materials before starting the roofing project. You don’t have to wait around for materials after you start laying the shingles. A roof shingle calculator gives you an accurate amount of shingles to order. Based on this figure you can order all other related items. When you prepare well in advance you job will move along smoothly and with out interruption. You also can finish it on time which gives more satisfaction than anything else.

A roof shingle calculator needs some preliminary data that is used to arrive at the number of shingles to order. Here we will explore two methods of calculating roofing shingles quantity to order. You also have to factor in extra roof shingles for wastage, overlapping and starter shingles.

There are certain roofing terms that you need to know when using the roof shingle calculator.

Square- This is a roofing term that refers to an area equal to 100 square feet in real terms. So, if you are buying a square of roofing shingles it means that it will cover 100 square feet of roof area.

Bundle – Shingles are wrapped in paper or plastic and sold in bundles. These bundles are light enough to be carried by any person. So, when buying heavier shingles you will need to order more bundles than when buying light-weight shingles. Usually the standard asphalt 3-tab shingles cover 3 square per bundle. There are about 29 shingles in bundle of size 12 inches by 36 inches. Heavier laminated and architectural shingles need 4-5 bundles to cover the same area.

So, now you know the basic terms used in roof shingle calculator. Next, most important step is to go measure your roof. You need to the area of your roof to order roof shingles. To measure the roof you can either measure it or use the sheet count method.


Get up on the roof measure each plane of the roof, get its length and width and calculate the area by multiplying the lenght and width of each of plane and adding them all up to arrive at the square footage of the roof to be used in the roof shingle calculator. If you have steep slopes then measuring the area is a little more complex. First measure the length of the building at the ground level and make provisions for any roof overhangs. Now, walk up a ladder and using a stiff measuring tape, measure the length of the slope from the eaves to the edge of the ridge.

Sheet Count Method:

In the other using the sheet count method to use in the roof shingle calculator, you just count the number of sheets needed to cover the whole area. It’s fast method and can be done from the ground. This can be only done with the sheathing is exposed and panels are of 4 feet by 8 feet are used as structural panels. Count the full panels and make a estimate about the ripped and crosscut sheets at the edges and make it up to a full sheet. If sheets are diagonally cut then assign them a size of say or half or quarter depending on the cut. As each sheet measures 32 feet area you can arrive at the square footage by adding up all the sheets you have counted.

How Much To Order?

If the roof shingles you are ordering are of the kind that cover 3 bundles to a square then it is easy to order one bundle for every sheet of roof sheathing you counted. If you are buying the heavier or lighter kind of bundles then just divdide the number of sheets of sheathing by 3. This gives you the total number of squares of sheet needed to cover the roof. The calculations are fairly simple and you can work it out yourself that three sheets of sheathing cover roughtly 100 square feet or one square in roofing terms.

All these measurements may seem very simplistic but you don’t have to be really that exact considering that there will be wastage of shingles and at the edges and corners you have to allow for good margin, you have to calculate for the overlapping and so on. If your roof shingles calculator allows for healthy margin for extra shingles then that might be quite enough. Else, you need to order more.

Take Into Account Wastage

Remember that you will need to order more than the just square foot area of the roof. Starter courses along the eaves and at rakes, extra shingles for ridges, hips and valleys all need more shingles than the area they cover. Also, in order to stagger the joints you have to cut the shingles by half a tab length for every row, this again will generate its own waste, against the walls and around chimneys and other vents, shingles will need to be cut to fit correctly. Some wastage is inevitable due to breakage, wrong cutting, improper nailing or tearing. So, add about 3 bundles of extra shingles to the value arrived at by your roof shingles calculator. If you are inexperienced you may need more than that.

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