Flatbed tarp sizes: get the width, drop and end flaps right
What dimensions decide the tarp size?
Measure the load width, the length to cover and the height above the deck. Trailer width alone does not describe what the tarp has to cover. A fleet that carries different load shapes needs a dimension sheet for each intended use.
Flat width needed = load width + twice the required drop. This is the drape arithmetic used by our flatbed tarp size calculator. It checks the published drop as well as overall width and length. End flaps and the arrangement of a multi-tarp set still need separate confirmation.
A worked example: overall size and drop are separate checks
Example inputs: a load 8.5 ft wide, 24 ft long and 5.5 ft high. Covering both sides to the deck needs a flat width of 8.5 + 2 x 5.5 = 19.5 ft.
The published 20 x 27 ft, 6 ft drop flap lumber tarp has enough overall width and length for those inputs, and its published 6 ft drop reaches past the load height. That is a dimensional comparison, not a complete order: the end flap, finished size and hardware must still be confirmed. The example does not add an allowance for overlaps or fixing.
Should you choose a lumber, steel or coil tarp?
Lumber tarps cover packaged lumber and tall palletized loads; their end flaps need particular attention. Steel tarps serve plate, beams, pipe and lower loads. Their name does not select a drop height: compare the actual dimensions below.
Coil tarps are shaped around coils. Specify coil diameter, width and eye orientation rather than applying a rectangular drape formula. Hay tarps have a different sizing problem again: the surface of the bale stack, for which the round bale stack calculator states its own assumptions.
Does a 6 ft or 8 ft drop cover your load?
Choose the required side coverage first. For an illustrative load 8 ft high, a 6 ft drop leaves 2 ft of each side uncovered; an 8 ft drop reaches the deck. A taller drop also requires more flat width. These are geometry checks, not advice on how to fasten a cover or secure cargo.
A label such as “6 ft drop” is not enough if the load is wider than the top panel. An 8.5 ft wide load requiring 6 ft on both sides needs 20.5 ft of flat width. A 20 ft wide sheet cannot meet both those dimensions even if the listing calls it a 6 ft drop tarp. Confirm how the seller defines the top panel and drop.
How do overlaps and end flaps change a two-tarp order?
Draw each piece over the portion of the load it will cover. Identify the front and rear faces separately, then mark the joint between pieces. Adding two catalog lengths does not prove that the set covers that much load: the overlap uses length, and material wrapping down an end may use it too.
Illustrative top coverage: if each piece actually provides 27 ft along the top and the joint overlaps by 4 ft, the combined top coverage is 27 + 27 - 4 = 50 ft. The overlap is an example input, not a recommended allowance. This calculation assumes end coverage has already been dealt with; it does not say that two nominal 27 ft listings cover that length.
There is a real reason to ask for the drawing. One US Cargo Control lumber listing states that its overall length includes a rain flap. A buyer comparing sizes needs the usable top length and the flap dimensions, not just the label. Market listing read October 3, 2026 (N2); no stock or matching Heavy Tarp Supply product is implied.
Put quantity per piece on the request. “Ten sets” is ambiguous until the number and layout of pieces in each set are stated. For mixed fleet loads, prepare a separate line for each configuration. Then calculate each piece's dimensional requirement; the calculator does not design an overlapping set.
Published lumber and steel tarp sizes
US vendor references read 2026-08-20, not our stock. Each linked specification names the listing behind the dimensions. A custom order confirms finished size rather than assuming that every listing defines its dimensions in the same way.
| Family | Published flat size | Published drop | Reference |
|---|---|---|---|
| Lumber Tarps | 16 x 28 ft | 4 ft | 16 x 28 ft, 4 ft drop specifications |
| Lumber Tarps | 20 x 18 ft | 6 ft | 20 x 18 ft, 6 ft drop specifications |
| Lumber Tarps | 20 x 27 ft | 6 ft | 20 x 27 ft, 6 ft drop flap specifications |
| Lumber Tarps | 20 x 28 ft | 6 ft | 20 x 28 ft, 6 ft drop specifications |
| Lumber Tarps | 24 x 18 ft | 8 ft | 24 x 18 ft, 8 ft drop specifications |
| Lumber Tarps | 24 x 28 ft | 8 ft | 24 x 28 ft, 8 ft drop specifications |
| Lumber Tarps | 24.5 x 27 ft | 8 ft | 24 ft 6 in x 27 ft, 8 ft drop specifications |
| Lumber Tarps | 28 x 28 ft | 10 ft | 28 x 28 ft, 10 ft drop specifications |
| Steel Tarps | 16 x 27 ft | 4 ft | 16 x 27 ft, 4 ft drop specifications |
| Steel Tarps | 20 x 18 ft | 6 ft | 20 x 18 ft, 6 ft drop specifications |
| Steel Tarps | 24 x 18 ft | 8 ft | 24 x 18 ft, 8 ft drop specifications |
What should the dimension sheet confirm before an order?
- The finished flat width and length, the side drop and the end flap placement.
- Which load each tarp covers, including overlaps if you order a set.
- Fabric weight per area, seam construction, D-ring rows and grommet spacing.
- The checks at reception against the same dimensions and specification.
Keep dimensions and fabric weight as separate checks. A correctly sized tarp can still use a fabric different from the one you ordered. The flatbed tarp specification checker prepares the fabric, construction and reception-check block; the size calculator prepares the dimensional comparison. Both can attach their result to a quote request.
If no published format fits, describe the required dimensions for a custom quote. Do not choose the closest label and leave the missing coverage for later.
First personal reply within 2 business days, with clarifying questions or next steps.