Shingles can be thought of or rectangles with an area of 3 sf, with a length of 3’ and a height of 1’, out of which only .5 inches are usually exposed
To calculate the amount of shingles needed for roofing square, follow these instructions
Example: What's the amount of shingles per square needed if you have 3' by 1' shingles with 5" of exposure.
Example: What's the amount of shingles per square needed if you have 4' by 1' shingles with 5" of exposure.