What Size Tarp Should You Order? Cut Size vs Finished Size Explained
The safest way to buy a made-to-measure tarp is to specify the coverage you need as a finished size, then let the fabricator calculate the larger raw cut needed for hems, welded seams, pockets and reinforcement. This guide shows how to measure the job, write the quotation basis and set a practical custom tarp size tolerance.
The practical answer
For an exact-fit or project tarp, ask the supplier to quote the finished dimensions after all hems and seams. Send the object measurements and required overlap or side drop as supporting information. Do not add an estimated hem loss yourself: the manufacturer should build that consumed material into the cutting plan. For a stock tarp with flexible coverage, confirm whether the listed size is cut size and expect the usable dimensions to be smaller.
Four dimensions are often compressed into one “tarp size”
A purchase order that says only “10 × 12 ft” can still produce two different expectations. The buyer may mean the area that must be covered, while the factory may read it as the fabric dimension before finishing. Separate these four measurements before comparing prices.
The item, frame or opening
The actual length, width, height, curvature and obstacles of what must be protected.
The area the tarp must reach
Object size plus useful overhang, side drop, fastening reach or weather overlap.
The completed usable tarp
Measured after hems, seams, reinforcement and edge fabrication are complete.
The raw production dimension
The larger panel size before material is consumed by folding, welding, sewing or pockets.
Which size basis should appear on the quotation?
The right answer depends on how precise the fit must be. A low-cost stock cover can tolerate a broad size range; a replacement curtain, machinery cover or OEM product normally cannot.
| Buying situation | Preferred quotation basis | Why it matters | What to put in writing |
|---|---|---|---|
| General stock tarp for loose coverage | Confirm cut or finished size | The label may describe material before hems, so actual coverage can be smaller. | Minimum acceptable finished length and width, or select the next suitable stock size. |
| Flat custom sheet with edge overlap | Finished size | The buyer needs a known final coverage area after edge finishing. | Finished L × W, overlap requirement, hem type and measurement condition. |
| Truck, trailer or cargo tarp | Finished size plus hardware drawing | Side drop and tie-down positions control installation more than top-deck dimensions alone. | Finished overall size, rail height, flap design, grommet/D-ring centers and reinforcement zones. |
| Machinery or box-shaped cover | Finished pattern dimensions | Handles, pipes, sharp corners, access flaps and three-dimensional shape affect fit. | Top and side views, finished panel dimensions, corner construction, openings and closures. |
| Canopy, frame or tensioned panel | Engineered finished dimensions | A tarp equal to the frame size may leave no tensioning gap and overload attachment points. | Frame dimensions, intended gap or tension, fixing system, diagonals and approved sample fit. |
| OEM/private-label repeat order | Controlled finished-size specification | Repeatability requires the same dimensions, hardware locations and packing identification. | Revision-controlled drawing, tolerances, inspection method, sample code and change approval process. |
Calculate a starting finished tarp size
Enter the top surface and the allowance required at each edge. For a flat cover, the allowance is overlap. For a draped equipment or cargo cover, it is the measured drop from the top edge to the desired tarp edge. The result is the finished size to request, not the factory cut size.
Enter your measurements
Use one unit consistently. Measure along the real surface for curved or sloped objects.
Recommended quotation dimension
State these as the required finished dimensions after fabrication. Also send the original object size so the supplier can check that the allowance matches the installation.
Flat cover
Add useful overlap to all four edges. Do not add factory hem allowance.
Finished L = surface L + front overlap + back overlap
Finished W = surface W + left overlap + right overlap
Equipment or cargo
Add measured side drops so the finished edge reaches the fixing line.
Finished L = top L + front drop + rear drop
Finished W = top W + left drop + right drop
Curved or sloped shape
Use a flexible tape along the actual surface and show the profile in a side-view drawing.
Use surface-path dimensions, not only horizontal projection
How much larger should the tarp be?
There is no single “add six inches” rule for every job. The additional size should come from an installation function: water runoff, full side coverage, tie-down reach, frame tension or overlap between adjacent sheets.
Pallet or flat outdoor stack
A 2.4 × 1.2 m top needs 0.3 m of overlap on every side. Request a finished tarp of 3.0 × 1.8 m.
The 0.3 m is usable overlap. The supplier separately adds the raw material required for the selected hem.
Rectangular equipment cover
Equipment is 3.0 m long and 1.8 m wide. The desired front/rear drop is 1.0 m, and each side drop is 1.2 m. Request approximately 5.0 × 4.2 m finished size for a simple draped sheet.
A fitted box cover needs a panel drawing rather than one flat dimension.
Truck or trailer load
Measure deck length and width, maximum cargo profile, bow or headboard height, side-rail location and the drop needed to reach straps or hooks.
Record rear flap and hardware locations separately; overall size alone cannot control fit.
How to make the supplier's size basis unambiguous
A clear quotation does more than label the dimension “finished.” It defines when, where and under what condition the measurement is taken. Flexible coated fabric can relax, stretch under tension and distort locally near welds or reinforced edges.
Put these details on the drawing
- Finished overall length and width after all seams and hems.
- Datum corners or reference edges used for measurement.
- Flat and relaxed, lightly tensioned, or fitted-to-frame measurement state.
- Hem depth, seam route, weld overlap, pockets and rope-in-hem details.
- Grommet, D-ring, strap, buckle or hook-and-loop center positions.
- Diagonal dimensions when squareness affects installation.
- Separate tolerances for overall size and local hardware positions.
Ask the quotation to confirm
- Whether the price covers roll goods, cut panels or completed tarps.
- Whether dimensions are cut size, finished size or nominal stock size.
- Material construction, target GSM, color and surface finish.
- Welded or sewn seams and the edge reinforcement method.
- Quantity, packaging format, labeling and drawing revision.
- Size tolerance and inspection sampling before packing.
- Prototype or pre-production sample approval for dimension-critical work.
Copy-ready quotation wording
Replace the example values and attachment references with your project information.
Quotation basis: FINISHED SIZE, not cut size
Finished dimension: 6000 mm (L) × 4000 mm (W), after all hems and welded seams
Measurement condition: Laid flat and relaxed on a level surface; no pulling or artificial tension
Measurement datum: Outer finished edge to outer finished edge at the four identified corners
Edge construction: Reinforced welded hem; details per Drawing DF-01 Rev. B
Hardware: Grommet centers and quantity per drawing; position tolerance stated separately
Overall size tolerance: To be proposed and confirmed in the signed quotation/specification
Material: PVC coated polyester, target GSM, and performance requirements to be confirmed
Approval: Identified pre-production sample required before bulk production
A tolerance number is useful only when the measurement method is fixed
There is no universal dimensional tolerance for every stock sheet, heavy-duty PVC tarp, fitted cover and tensioned panel. Material type, overall size, number of seams, welding or sewing route, edge reinforcement, temperature, shape and required fit all influence what is practical. The accepted range should be reviewed before sampling and written into the commercial specification.
Useful for large overall dimensions
A percentage scales with the tarp size, but it must say how rounding works and whether every individual tarp or only a lot sample must comply.
Useful for local positions
Millimeters or inches are often clearer for grommet centers, pocket positions, flap lengths and other features where a percentage would be too broad.
Useful when undersize is critical
A minimum finished width or coverage limit can protect an installation where a small positive excess remains usable but any negative variation creates a gap.
| Control item | Why a separate limit may be needed | Recommended measurement note |
|---|---|---|
| Overall finished length and width | Controls usable coverage and fit after all fabrication. | Measure flat and relaxed from defined outer-edge datums. |
| Diagonals / squareness | A rectangle can meet length and width but still rack out of square. | Measure both corner-to-corner diagonals on the same flat surface. |
| Grommet or D-ring centers | Small position errors can prevent alignment with hooks or rails. | Measure from one fixed datum; do not accumulate spacing error from hole to hole. |
| Seam and pocket positions | These can affect water path, folding, frame alignment or insertion of poles and ropes. | Show centerline or finished-edge position on the approved drawing. |
| Fitted shape and openings | Three-dimensional covers may pass a flat overall check but fail at corners or access points. | Use a sample fitting, reference frame or dimensional inspection fixture where appropriate. |
Any numerical examples discussed during sourcing should be treated as project-specific proposals, not as a universal industry promise. Final feasible tolerances should be confirmed against the selected material, design, sample and production method.
Size planning should connect material, finishing and repeat-order control
Built around the buyer's application and drawing
DERFLEX supports professional buyers sourcing PVC coated polyester materials and custom tarps for transportation, construction, industrial equipment, agriculture, storage and OEM/private-label programs. Available directions can be discussed according to order requirements and production feasibility.
Approx. 300–1200 GSM PVC tarpaulin directions, subject to the selected construction and application.
Welded or sewn seams, reinforced hems, corner patches, pockets, webbing and rope edges.
Grommets, D-rings, straps, buckles and other hardware positioned to an agreed drawing.
Color, printing, labels, packaging and repeat-order identification can be reviewed for bulk programs.
Finished size is only one part of usable fit
A tarp can have the correct overall dimensions and still be difficult to install if hardware spacing, seam direction, corner reinforcement or side drop does not match the job. For a dimension-critical cover, combine the size drawing with material and fabrication details.
- Choose a material weight and structure appropriate for handling, wind, abrasion and outdoor exposure.
- Place seams where they do not interfere with drainage, folding, visibility or high-wear contact points.
- Reinforce the edge and corners according to the actual tie-down load rather than using grommets alone.
- Confirm how the tarp will be folded and packed so hardware and coated surfaces are protected in transit.
A practical custom tarp sizing workflow
This process reduces the chance that a price comparison is based on different dimensions or different levels of finishing.
Measure the job
Record outermost length, width, height, curves, protrusions, fixing line and environmental exposure.
Define coverage
Add only the overlap, side drop, clearance and tensioning allowance needed by the installation.
Issue a drawing
Mark finished dimensions, datums, seams, hems, pockets, hardware centers and drawing revision.
Confirm the quote
Check size basis, material, finishing, tolerance, sample plan, quantity, packing and delivery terms.
Approve and control
Approve an identified sample, retain measurement records and use the same specification for repeats.
Continue from sizing into material and specification decisions
These six internal guides help buyers complete the information needed for an accurate custom tarp inquiry.
Cut size, finished size and tolerance FAQ
Should I order a tarp by cut size or finished size?
Use finished size when the tarp must provide a defined coverage area or fit a vehicle, machine, frame, opening or repeat-order product. Cut size is mainly a raw production or stock-listing reference before hems, seams and reinforcement consume material.
Is the quoted tarp size normally the finished size?
Not always. Stock tarps are often described by cut size, while custom industrial covers may be quoted by finished size. Ask the quotation to state “finished size after all hems and seams” and define how the completed tarp will be measured.
How much larger should a tarp be than the object?
Add the drop, overlap and tie-down reach required by the installation. For a flat cover, add overlap to both ends and both sides. For equipment or cargo, measure over the actual top and side surfaces. Avoid adding arbitrary excess that can create flapping, water pockets or difficult handling.
Do I add hem allowance to the finished tarp size?
No. When you order by finished size, state the usable final dimensions. The fabricator should work backward and add the raw material needed for perimeter hems, weld overlaps, pockets, rope edges and reinforcement. Adding another estimated hem allowance can make the completed tarp too large.
What is a reasonable custom tarp size tolerance?
There is no single tolerance for every tarp. Feasible limits depend on material, finished dimensions, number and direction of seams, welding or sewing, reinforcement, shape and measurement condition. Agree the numerical range, datum points, flat or tensioned state and inspection sampling before production.
What should I send DERFLEX for a more accurate quotation?
Send object dimensions, required finished dimensions, a drawing or photos, application and exposure, material or GSM direction, hem and reinforcement design, grommet or D-ring positions, quantity, color, printing, packaging and the proposed tolerance and inspection method.
Need a custom tarp size checked before quotation?
Send DERFLEX the object dimensions, desired finished coverage, side drops or overlap, application photos, fixing method, quantity and target material direction. The team can review the size basis and fabrication details for a project-specific quotation.