Identify how the tarp mounts, travels, and closes before choosing dimensions. Measure the body opening and the loaded profile, then add only the overlap required by the rail, roller, bow, or tie-down arrangement.
Truck tarp sizing is not simply “bed length × bed width.” A dump-body tarp may roll from front to rear over bows. A side-roll system crosses the body. A pickup cover may drape over a stationary load. The same truck dimensions can require different tarp dimensions.
What to measure
- Inside and outside body length: note the front cap, tailgate, and any hardware that shortens the usable opening.
- Body width: measure the opening and the outside rail-to-rail distance.
- Highest loaded profile: measure above the bows or load, not only the sidewall height.
- Travel path: follow the route the tarp actually takes from roller to landing point.
- Mounting zones: record roller width, axle location, pockets, hooks, and protected clearances.
Use a rigid tape for the body and a flexible tape or non-stretch line over the loaded profile. Do not climb onto unstable cargo to take a measurement.
Dump truck and dump trailer tarps
For a front-to-rear roll system, tarp width is usually governed by body width, bow rise, and the amount needed to reach the side rails without excessive hanging material. Length is governed by the roller position, body length, tailgate geometry, and the system’s required wrap or closure.
Measure along the centerline over the bows from the roller attachment area to the rear landing point. Then measure cross-body over the highest bow. Compare these measurements with the system manufacturer’s replacement-tarp instructions. Roller systems impose loads and attachment details that a generic flat tarp may not be designed to accept.
Replacement tarp rule
When replacing a tarp in an existing mechanical system, use the system model and the old tarp’s attachment pattern as evidence—but remeasure the body. A stretched, torn, or incorrectly fitted old tarp is not a reliable template by itself.
Pickup and utility truck beds
For a simple draped cover, measure the load footprint at its widest and longest points. Add two drops when the tarp must reach down both sides, plus enough allowance to secure below the widest part. A load that rises above the cab or tailgate changes the profile dramatically.
Do not attach to trim, plastic caps, sharp sheet metal, hot exhaust parts, steering components, or anything not rated for the force. Loose fabric can obscure lights, the license plate, mirrors, or the driver’s view.
Bows, overlap, and wind
Bows prevent deep water pockets and support the fabric, but they increase the cross-body distance. Measure over the bow arc instead of adding bow height as a simple vertical number. A flexible tape laid over the actual bow gives the most direct measurement.
More overlap is not automatically safer. Excess material can flap, wear against rails, interfere with moving parts, or create a large wind-catching fold. Use the overlap specified for the tarp system and distribute tension across reinforced areas rather than pulling hard on isolated grommets.
Cargo securement and safe operation
A weather tarp may help contain fine material when used in an appropriate system, but it does not automatically replace required tiedowns, blocking, bracing, or other cargo-securement components. Commercial operations in the United States should follow applicable requirements in 49 CFR Part 393, Subpart I, carrier procedures, and equipment instructions.
- Park away from traffic on stable ground before measuring or adjusting.
- Keep clear of powered rollers, springs, arms, and stored energy.
- Do not stand on unsecured loads or body rails.
- Check clearance before operating under power lines or structures.
- Repair tears and loose hardware before fabric can enter wheels or traffic.
Measurement worksheet
| Measurement | Your value | Why it matters |
|---|---|---|
| Body opening length | _____ ft _____ in | Base travel distance |
| Body outside width | _____ ft _____ in | Rail-to-rail coverage |
| Distance over bows | _____ ft _____ in | True cross-body path |
| Roller to rear landing point | _____ ft _____ in | System length |
| Specified side overlap | _____ in | Closure and containment |
How this guide was prepared
We separate geometry and unit conversions from product claims, use exact standards where available, and flag specifications that vary by manufacturer. See our editorial policy for the review process.