Tarp Specification Guide

Tarp Thickness Explained: Mils, GSM, and Ounces Guide

Q: Is 10 mil the same as 10 mm?

No. 10 mil equals 0.010 inch, which is 0.254 mm. Mil is not an abbreviation for millimeter.

Q: How many GSM is an 18 oz tarp?

18 ounces per square yard is approximately 610 GSM. This converts area weight only and does not establish an exact mil thickness.

Q: How many GSM is a 22 oz tarp?

22 ounces per square yard is approximately 746 GSM. Actual physical thickness depends on the material construction.

Q: What is considered a heavy-duty tarp thickness?

There is no universal heavy-duty threshold across every tarp material. Compare like-for-like material, thickness or area weight, reinforcement, seams and intended service conditions.

Q: What should I compare when two tarps have the same 20 mil thickness?

Compare material family, GSM or ounce weight, base fabric, denier and weave, tensile and tear properties, coating, UV and cold requirements, seams, hems and hardware reinforcement.

Mil and millimeter measure thickness. GSM and ounces per square yard measure material mass per area. They answer different questions, so there is no universal conversion from GSM or ounces to mil thickness.

This guide helps distributors, fabricators, fleet operators, contractors and industrial buyers compare tarp specifications correctly across PE, PVC/vinyl, canvas, mesh and clear flexible sheet products.

Mil ? mm GSM ? oz/yd2 18 oz / 22 oz / 40 oz PVC & PE Comparison B2B RFQ Checklist

Request a Tarp Specification Review Choose a Tarp by Mil Range

AI Overview / Featured Snippet Answer

What do mils, GSM and ounces mean on a tarp?

Mil measures physical thickness; GSM and oz/yd2 measure finished material weight per area. A 20 mil tarp is 0.020 inch thick, while an 18 oz tarp weighs about 18 ounces per square yard, or approximately 610 GSM. These numbers are not interchangeable.

For purchasing, compare mil with mil, GSM with GSM, or convert GSM ? oz/yd2. Then check the base fabric, coating, tensile and tear properties, seam method, reinforcement and intended use. For a separate application-first chart, use the DERFLEX tarp mil thickness guide.

Understand the Specification

Four Units, Four Different Meanings

The first sourcing mistake is treating every number as a thickness grade. The correct interpretation depends on what the unit actually measures.

mil

Physical thickness

One thousandth of an inch. Common in North American poly tarp, vinyl sheet and finished tarp listings.

Metric thickness

Physical thickness in millimeters. Frequently used on technical data sheets for coated fabrics and flexible sheets.

GSM

Mass per square meter

Grams per square meter. Useful for coated fabric weight, purchasing, roll comparison and finished-cover weight estimates.

oz/yd2

Mass per square yard

Common in North American vinyl and canvas markets. Confirm whether the supplier states finished coated/treated fabric weight.

Related specification: Denier (D), such as 500D, 1000D or 1300D, describes yarn linear mass. It does not equal finished tarp thickness or finished area weight. If you are comparing the whole tarp rather than only its units, see the DERFLEX tarpaulin buying guide.

Exact Unit Conversions

Mil-to-mm and GSM-to-oz Conversion Charts

These conversions are mathematical. They do not predict strength, coating quality, reinforcement or service life.

millimeters = mil × 0.0254

Mil	Inches	Millimeters	Micrometers
3 mil	0.003 in	0.076 mm	76.2 μm
5 mil	0.005 in	0.127 mm	127 μm
6 mil	0.006 in	0.152 mm	152.4 μm
8 mil	0.008 in	0.203 mm	203.2 μm
10 mil	0.010 in	0.254 mm	254 μm
12 mil	0.012 in	0.305 mm	304.8 μm
14 mil	0.014 in	0.356 mm	355.6 μm
16 mil	0.016 in	0.406 mm	406.4 μm
18 mil	0.018 in	0.457 mm	457.2 μm
20 mil	0.020 in	0.508 mm	508 μm
22 mil	0.022 in	0.559 mm	558.8 μm
24 mil	0.024 in	0.610 mm	609.6 μm
30 mil	0.030 in	0.762 mm	762 μm
40 mil	0.040 in	1.016 mm	1016 μm

oz/yd2 = GSM ÷ 33.9057

GSM	Approx. oz/yd2	GSM	Approx. oz/yd2
90	2.65 oz	450	13.27 oz
120	3.54 oz	550	16.22 oz
150	4.42 oz	610	17.99 oz
200	5.90 oz	650	19.17 oz
250	7.37 oz	680	20.06 oz
300	8.85 oz	750	22.12 oz
340	10.03 oz	900	26.54 oz
1000	29.49 oz	1200	35.39 oz

Do not use a “GSM-to-mil conversion chart” as a universal rule. A tarp is often a composite of woven reinforcement, coating or lamination, surface finish and void space. Two constructions can have the same GSM but different thickness, or the same thickness but different GSM and tear behavior.

Built-In Buyer Tools

Convert Units and Estimate Material Weight

The static formulas above remain visible without JavaScript. These calculators are an optional convenience for buyers preparing specifications or freight estimates.

Mil / mm Converter

Mil

Millimeters

20 mil = 0.0200 in = 0.508 mm

Formula: 1 mil = 0.001 inch = 0.0254 mm.

GSM / oz/yd2 Converter

GSM

oz/yd2

610 GSM ≈ 17.99 oz/yd2

This conversion compares area weight only. It does not estimate mil thickness.

Finished Tarp Material Weight Estimator

Length

Width

Dimension unit

Material GSM

Approx. sheet material weight: 39.0 kg / 86.0 lb

Estimate excludes hems, overlap, webbing, ropes, hardware, patches, seams, packaging and manufacturing tolerances.

Material-Specific Reading

Which Tarp Specification Matters Most by Material?

Thickness is useful, but different tarp families are sold and engineered using different combinations of units.

Material family	Common specification language	What the buyer should verify	Why one number is not enough
PE / poly tarp	Mil, GSM, denier, weave/mesh count	Finished mil, woven core, lamination, UV treatment, grommet and corner reinforcement	A thicker PE surface can still fail if the woven reinforcement or tie-down construction is weak.
PVC / vinyl coated polyester	GSM or oz/yd2, mm or mil, denier, weave density	Base fabric, coating build, adhesion, tensile/tear targets, weldability, UV/cold formulation and finishing	PVC tarps are composite technical textiles; weight, thickness and reinforcement must be read together.
Canvas tarp	oz/yd2, weave, fiber/treatment	Whether weight is untreated or finished, water-resistant treatment, breathability, shrinkage and sewing details	Canvas is commonly selected for breathability, so a direct mil comparison with plastic-coated tarps can be misleading.
Mesh tarp	GSM, denier/yarn, openness or shade factor	Airflow, open area, tear strength, edge reinforcement and intended wind behavior	Open structure is intentional; physical thickness alone says little about the useful performance.
Clear vinyl / flexible sheet	Mil or mm first	Actual film thickness, clarity, flexibility, temperature behavior, formulation and reinforcement if present	A thick clear sheet may not contain the woven scrim used in an opaque industrial tarpaulin.

For reusable waterproof industrial covers, DERFLEX offers PVC tarp materials and finished-cover options in multiple GSM, thickness and fabrication directions. Exact suitability should be confirmed against the application and approved sample.

North American Vinyl Reference

10 oz, 13 oz, 18 oz, 22 oz and 40 oz: What Do They Mean in GSM?

Ounces per square yard convert directly to GSM. They still do not tell you an exact mil thickness unless the specific material construction is known.

10 oz≈ 339 GSMlighter vinyl direction

13 oz≈ 441 GSMmid-weight vinyl direction

18 oz≈ 610 GSMcommon heavy-duty vinyl class

22 oz≈ 746 GSMheavier-duty vinyl class

40 oz≈ 1,356 GSMhigh-mass specialty direction

Why 18 oz does not equal one exact mil value

Two 18 oz coated fabrics can use different polyester scrims, coating ratios, PVC formulations, embossing and surface finishes. Their total mass per area can match while their physical thickness differs.

What to request with an ounce grade

Ask for the finished GSM/oz weight, actual thickness, base fabric construction, tensile and tear data, coating/lamination method, service temperature direction, UV requirement and finishing method.

Measurement Quality

Where and How Should Tarp Thickness Be Measured?

The number is only meaningful when the measurement location and method are consistent.

Measure the body, not the hem

Check the working sheet away from folded hems, welded overlaps, seams, corner patches and hardware zones. Reinforced areas are intentionally thicker.

Use controlled contact

A thickness gauge or micrometer gives a more repeatable result than squeezing the material with a hand caliper. Contact pressure, surface texture and yarn crossover can influence the reading.

Ask for tolerance and method

For repeat B2B procurement, request a defined thickness tolerance and a consistent inspection method rather than relying on a single nominal marketing number.

Important: A stated “20 mil” value does not prove tensile strength, tear resistance, coating adhesion or finished tarp durability. Those properties require their own specification or test data.

B2B Procurement Logic

How to Compare Two Tarp Quotations Without Buying the Wrong Grade

Use the same specification basis for every supplier. Otherwise a lower price may simply describe a lighter or differently constructed tarp.

Match the material family

Compare PE with PE or PVC-coated polyester with PVC-coated polyester before interpreting thickness or weight.

Normalize the units

Convert oz/yd2 to GSM and mil to mm so both quotations use the same measurement system.

Check finished vs nominal values

Confirm that weight and thickness refer to the finished coated/laminated material, not an intermediate layer or a maximum point.

Compare the reinforcement

Review denier, weave density, tensile and tear performance, edge webbing, hems, corner patches and hardware load paths.

Compare fabrication assumptions

Welding, sewing, overlap width, grommet spacing, D-rings, pockets and local wear pads can change both performance and price.

Compare service conditions

UV exposure, cold flexibility, abrasion, chemicals, road wind, repeated folding and intended service cycle should be part of the brief.

If the application involves repeated handling, strong tie-down loads or industrial exposure, review DERFLEX heavy-duty tarp construction options rather than choosing only by mil or GSM.

Application Decision Matrix

Start with the Job, Then Select the Numbers

The ranges below are practical discussion points, not universal grades. Final specifications depend on material structure, exposure, fabrication and approved sample.

Application direction	Useful first specification	Then verify	Buyer note
Temporary PE covering	Mil + GSM	Weave, UV duration, corners, grommet retention	Portable and economical may matter more than maximum mass.
General outdoor storage	Mil for PE; GSM/mm for coated fabric	UV, water shedding, abrasion, condensation, fastening	Do not over-specify thickness if the main failure is poor anchoring.
Industrial PVC cover	GSM/oz + mm/mil	Base fabric, coating adhesion, tensile/tear, weldability, finish	450–900 GSM is a common DERFLEX heavy-duty PVC discussion range; the exact build is application-dependent.
Truck / trailer tarp	GSM/oz + base fabric + thickness	Road wind, cargo abrasion, repeated folding, seams, webbing, D-rings/grommets	Transport duty should be engineered around the complete load path, not a single weight number.
Clear flexible sheet	Mil or mm	Clarity, formulation, cold flexibility, reinforcement if required	A 30–40 mil clear sheet is not automatically comparable to a reinforced woven tarp.

Common Procurement Mistakes

Six Tarp Thickness Mistakes That Distort Supplier Comparisons

Reading mil as millimeter

10 mil is 0.254 mm, not 10 mm. “Mil” is a thousandth of an inch.

Treating oz as total tarp weight

In many tarp listings, oz means ounces per square yard. A 10 × 20 ft finished tarp weighs far more than “18 ounces.”

Converting GSM directly to mil

There is no universal ratio for composite tarps because density, scrim and coating structure vary.

Using “heavy duty” as a standard

Marketing duty labels are not universal technical grades. Compare measurable specifications.

Ignoring where thickness is measured

A folded hem or overlap can be multiple layers thick and does not represent the working sheet body.

Assuming thicker always lasts longer

Wind, UV, abrasion, seams, grommets and base-fabric strength can control service life before body thickness does.

DERFLEX Image Pack

See Weight, Coating, Fabrication and Application in Context

Real product and manufacturing images help buyers understand why thickness is only one layer of the full tarp specification.

DERFLEX PVC coated fabric production line for industrial tarpaulin material — Manufacturing view: the final tarp specification starts with base fabric, coating and process consistency.

Blue heavy duty PVC tarpaulin surface and reinforced material close-up — Material close-up: thickness, area weight and textile reinforcement work together.

DERFLEX 18 ounce vinyl tarps with reinforced hems and grommets — Finished vinyl tarp: 18 oz describes area weight; hems and hardware are separate design variables.

PVC truck tarpaulin side curtain application on commercial trailer — Truck use: road wind, cargo friction and repeated fastening make reinforcement as important as GSM.

DERFLEX PVC tarpaulin rolls in multiple colors and coated fabric constructions — Roll-goods view: compare finished GSM, actual thickness, base cloth and surface finish before approving a grade.

RFQ Checklist

What to Send DERFLEX for a Tarp Thickness Recommendation

A complete inquiry makes it easier to match the material to the failure risk instead of simply supplying a heavier number.

1. Application & environment

Truck, construction, equipment, agriculture, storage or other use; indoor/outdoor; wind, rain, UV, cold, heat, abrasion and chemical exposure.

2. Material & target units

Preferred PVC, PE, canvas, mesh or clear sheet; current mil/mm or GSM/oz target; existing sample or technical data sheet if available.

3. Finished construction

Dimensions, seams, hems, webbing, rope edges, grommet spacing, D-rings, pockets, straps, wear patches, printing and packing requirements.

Frequently Asked Questions About Tarp Mils, GSM and Ounces

Short, direct answers for searchers and procurement teams comparing tarp specifications.

What does mil mean on a tarp?

Mil is a unit of physical thickness equal to one-thousandth of an inch. One mil equals 0.001 inch or 0.0254 mm. A 20 mil tarp is 0.020 inch, or about 0.508 mm, thick.

Is 10 mil the same as 10 mm?

No. 10 mil equals 0.010 inch, which is 0.254 mm. The word “mil” is not an abbreviation for millimeter.

Can tarp GSM be converted to mil?

Not with one universal formula. GSM measures mass per square meter and mil measures physical thickness. The relationship depends on material density, woven reinforcement, coating build, lamination, surface finish and construction.

How many GSM is an 18 oz tarp?

18 oz/yd2 is approximately 610 GSM. This is a direct area-weight conversion and does not establish an exact mil thickness.

How many GSM is a 22 oz tarp?

22 oz/yd2 is approximately 746 GSM. Ask the supplier for actual thickness and base-fabric construction if those properties matter to your application.

Does higher GSM always mean a thicker tarp?

No. Higher GSM means more mass per area, but thickness also depends on material density, scrim, coating ratio and surface construction. Two tarps can have similar GSM and different thickness.

What is considered a heavy-duty tarp thickness?

There is no universal heavy-duty threshold across all materials. PE products are often discussed by mil, while PVC/vinyl products are commonly specified by GSM or oz together with thickness and textile reinforcement. Compare like-for-like materials and the complete construction.

What does 1000D mean on a tarp?

1000D refers to denier, a measure of yarn linear mass used in the woven reinforcement. It is not the finished tarp thickness or the finished GSM. Weave density and coating must also be considered.

What should I compare when two tarps have the same 20 mil thickness?

Compare material family, GSM or oz weight, base fabric, denier/weave, tensile and tear properties, coating or lamination, UV/cold requirements, seams, hems and hardware reinforcement. Same mil does not mean same finished performance.

Turn Tarp Numbers into a Buildable Specification

Send DERFLEX your application, current material or sample, target mil/mm or GSM/oz, finished size, exposure, reinforcement layout, quantity and destination. The team can discuss a practical PVC coated fabric or finished tarp direction for quotation and sample review.

Request A Quote View PVC Tarp Options

Technical note: unit conversions on this page are mathematical. Material and application ranges are purchasing guidance, not universal engineering ratings. Final suitability should be confirmed against the actual service environment, approved material sample, finished-cover construction and any applicable project requirements.