How the tarp size calculation works
For a flat cover, the calculator adds your selected allowance to both ends and both sides. For a three-dimensional object, it also adds two full height drops. For a gable roof, it calculates the sloped distance over both roof faces from the building span and pitch.
Minimum size is not the same as a labeled stock size
The minimum result is the geometry of your measurements. The recommended result is the smallest size in our common-size list that fits both dimensions. A manufacturer’s “cut size” may be slightly larger than its finished, hemmed size, so check the product specification before buying.
How to measure
- Measure the longest point and the widest point, including handles, stacks, corners, or other protrusions.
- For equipment, measure from the top down to the lowest point you want covered. Use that value as the height.
- Add enough allowance for tie-down placement, overlap, and imperfect centering. Do not rely on a tight geometric fit outdoors.
- Compare the final minimum with the manufacturer’s finished dimensions—not only the size printed in the product name.
Which calculation mode should you use?
| Mode | Use it for | What it adds |
|---|---|---|
| Flat Cover | Ground sheets, flat stacks, simple rectangular areas | End and side allowance |
| 3D Object | Equipment, furniture, machinery, box-shaped loads | Two height drops plus allowance |
| Roof Area | Simple symmetrical gable roofs | Two slopes based on span and pitch, plus edge allowance |
Important limits
This calculator assumes straight rectangular measurements and, in roof mode, a symmetrical gable. Irregular loads, sharp corners, chimneys, complex roofs, high-wind exposure, and structural repairs require additional planning. A tarp is not a substitute for a designed roofing system or compliant cargo securement.