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Tarp Size Calculator: What Size Tarp Do I Need?

Calculate what size tarp you need for hay bales, flatbed trucks, pools, and ground cover. Recommends the nearest standard tarp size automatically.

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Units:

What are you covering?

Recommended: 2 ft / 0.6 m
93% found this helpful

How to Use This Calculator

  1. 1

    Select use case

    Choose Flat / Ground Cover (pool, patio, ground sheet), 3D Object Cover (woodpile, equipment, furniture), or Hay / Silage Stack.

  2. 2

    Enter dimensions

    Flat: length and width of the area. 3D object: length, width, and height of the item. Hay stack: length, width, and height of the full bale stack.

  3. 3

    Set overhang

    Enter the ground overlap on each side. Default: 2 ft for flat cover, 1 ft for 3D object, 2 ft for hay. Hay tarps: use 2–3 ft so excess can be tucked under the bottom bale row.

  4. 4

    Read tarp size and recommendation

    The calculator shows the exact tarp dimensions needed and highlights the nearest standard tarp size available from most retailers.

What Each Value Means

Coverage Length / Width (feet or metres)
The actual area you need the tarp to cover (flat) or the footprint of the object (3D). NOT the tarp size — the tarp must be larger to include overhang. Measure the object or area at its longest and widest points.
Object Height (feet or metres)
For 3D coverage: how tall the item is. The tarp must drape over the top and down each side, so height is added twice to both dimensions. A 4-foot woodpile needs 8 extra feet of tarp (4 ft down each side).
Overhang / Ground Overlap (feet or metres)
How much tarp extends beyond the object onto the ground on each side. More overhang = better wind protection and water runoff clearance. Standard: 2 ft per side for most uses. Hay tarps: 2–3 ft to allow tucking under the bottom bale row.

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Frequently Asked Questions

How do I calculate what size tarp I need?
For flat coverage: tarp = object length + (overhang × 2) by object width + (overhang × 2). For covering a 3D object (woodpile, hay stack): tarp length = object length + (height × 2) + (ground overlap × 2). Tarp width = object width + (height × 2) + (ground overlap × 2).
What size tarp do I need for a hay stack?
Measure your stack: length × width × height. Formula: tarp length = stack length + (height × 2) + 4 ft tuck-under (2 ft per side). Tarp width = stack width + (height × 2) + 4 ft. Example: 30×20 ft stack, 10 ft high = (30+20+4)×(20+20+4) = 54×44 ft tarp needed.
What are standard tarp sizes?
Common US standard tarp sizes in feet: 6×8, 8×10, 8×12, 10×12, 10×20, 12×16, 12×20, 16×20, 20×30, 20×40, 25×40, 30×40. Most hardware and farm stores stock up to 20×30. Larger tarps (30×50, 40×60) are available from specialty suppliers.
How much overhang should a tarp have?
Flat coverage (pool, ground sheet): 2 feet overhang per side minimum. 3D objects (woodpile, equipment): 1 foot ground overlap. Hay and silage stacks: 2–3 feet tuck-under per side — the extra tarp is weighted down by the bales themselves to resist wind.
What size tarp for a 20×40 ft pool?
Pool tarp = 20 + (2×2) = 24 ft wide, 40 + (2×2) = 44 ft long. Nearest standard: no exact match — use a 25×50 or overlap two 20×30 tarps. For precise pool covers with cable systems, order a custom-cut cover matched to pool shape.
What type of tarp is best for hay bales?
UV-stabilized polyethylene (PE) tarps rated for outdoor use. Look for 5–6 mil thickness, reinforced grommets, and a UV inhibitor additive. Silage-specific tarps (polyethylene silage film) are thinner but UV-optimized and are one-season use. Vinyl tarps last longer but cost more.

References & Sources

  1. [1]
    OSHA — Construction Tarp Requirements (opens in new tab)

    Supports: Evidence used for standard tarp sizes guide: available sizes and uses, including related formulas, definitions, or reference values.

    Verified

  2. [2]
    US Department of Agriculture — Hay Storage Best Practices (opens in new tab)

    Supports: Evidence used for tarp size formula: how to calculate the right tarp dimensions, including related formulas, definitions, or reference values.

    Verified

  3. [3]
    FMCSA — Federal Motor Carrier Safety Administration Cargo Securement Rules (opens in new tab)

    Supports: Evidence used for how to calculate flatbed tarp size: truck and trailer coverage guide, including related formulas, definitions, or reference values.

    Verified

  4. [4]
    US Forest Service — Emergency Shelter Tarp Use (opens in new tab)

    Supports: Evidence used for how to choose the right tarp size: buying guide for every use, including related formulas, definitions, or reference values.

    Verified