How to Calculate Cooler Bag Capacity in Liters and Cans

Cooler bag capacity is usually shown in liters, quarts, or the number of cans the bag can hold. These figures are related, but they do not mean the same thing.

A 20-liter rating describes internal volume, but it does not tell you exactly how many canned drinks will fit. Insulation thickness, rounded corners, zipper opening, can size, and the amount of ice all affect the usable space.

For a simple rectangular compartment, use this formula:

Capacity in liters = internal length × internal width × internal height in centimeters ÷ 1,000

This gives the estimated internal volume. The final can count should still be checked by packing a finished sample with the exact cans and cooling material the buyer plans to use.

If you remember only three things, use internal dimensions to calculate liters, never convert liters directly into cans, and verify the final can count with a finished sample.

Liters, Usable Capacity, and Can Capacity Are Different

Before calculating anything, it helps to separate three common capacity terms.

These figures may not be identical.

For example, a cooler may have a calculated internal volume of 20 liters but provide less usable space because its sides taper inward. Its can count will also depend on whether the cans are packed upright or horizontally and whether ice is included.

For an OEM project, the buyer and supplier should agree on which capacity figures will appear in the product specification, catalog, label, and retail packaging.

1. Use Internal Dimensions, Not External Dimensions

For an OEM specification, capacity should normally be calculated from the inside of the main insulated compartment unless the buyer and supplier have agreed on another measurement method.

Do not multiply the bag’s external length, width, and height. External measurements also include:

• Exterior fabric
• Insulation foam
• Lining
• Piping or binding
• Reinforcement
• Front and side pockets
• Structural panels

A cooler with thick insulation may look large outside but offer much less space inside.

Measure the finished compartment while the bag is standing in its normal shape. Do not stretch the fabric or force the walls outward to obtain a larger figure.

For a rectangular compartment, measure:

• Internal length
• Internal width
• Usable internal height

Measure the usable height only up to the normal closure line. Space above the zipper or beneath a curved lid may not be fully usable.

2. Calculate Capacity in Liters

One liter equals 1,000 cubic centimeters. The International Bureau of Weights and Measures defines a liter as one cubic decimeter.

When Measurements Are in Centimeters

Use:

Internal length × internal width × internal height ÷ 1,000 = liters

Calculation Example

Suppose a finished cooler compartment measures:

• Internal length: 35 cm
• Internal width: 22 cm
• Usable height: 25 cm

The calculation is:

35 × 22 × 25 ÷ 1,000 = 19.25 liters

The estimated internal volume is therefore 19.25 liters.

This does not mean that 19.25 liters of packaged food and drinks will fit. Rounded corners, inward-facing seams, a narrow zipper opening, and flexible walls may reduce the usable capacity.

This is a calculation example only, not a capacity claim for a specific Vancharli Outdoor product.

When Measurements Are in Millimeters

Use:

Length × width × height ÷ 1,000,000 = liters

When Measurements Are in Inches

Use:

Length × width × height × 0.016387 = liters

Useful Unit Conversions

When selling in both North America and Europe, it can be helpful to include liters and US quarts. Make sure both figures are based on the same internal volume.

3. Treat Tapered and Irregular Bags as Estimates

Many cooler bags are not perfect rectangles. Tote-style coolers may be wider at the top, while RF-welded soft coolers often have rounded corners and curved walls.

Irregular and strongly tapered cooler bags are difficult to calculate accurately by hand. During early development, the rectangular formula can provide a rough estimate using average internal dimensions. However, the final capacity should be confirmed with CAD data or a finished sample.

A hand calculation becomes less reliable when the bag has:

• Strongly curved panels
• Large rounded corners
• An irregular base
• A narrow opening
• Internal dividers
• Foam that changes shape when filled

For these designs, avoid presenting a hand calculation as the final usable capacity.

4. Do Not Convert Liters Directly Into Cans

A common mistake is to divide the cooler’s capacity by the liquid volume of one can.

For example, dividing 20 liters by 0.355 liters appears to suggest that a 20-liter cooler could hold more than 56 cans of 355 mL. That result is not realistic.

The calculation fails because:

• A can occupies more space than the liquid volume printed on its label
• Round cans leave empty spaces between them
• The cooler has seams and rounded corners
• The zipper opening may be smaller than the compartment
• Cans may not fit evenly across the length and width
• Ice or ice packs take up additional space

Liters describe volume. Can capacity describes how many physical containers can be packed into a particular shape. They should not be treated as a direct conversion.

5. Define the Reference Can First

Cans are not the same size in every market. Common beverage volumes include:

• 250 mL slim cans
• 330 mL cans
• 355 mL or 12 US fl oz cans
• 375 mL cans
• 473 mL or 16 US fl oz cans
• 500 mL cans

Even cans with the same liquid volume can have different heights and diameters.

Before calculating or testing can capacity, specify:

• Can volume
• Can diameter
• Can height
• Can style
• Target market
• Upright or horizontal packing
• Whether ice is included

For the most reliable result, the buyer can provide an actual reference can or a technical drawing showing its external dimensions.

6. Estimate the Number of Cans

For a rectangular cooler with cans packed upright, a simple grid calculation can provide an early estimate.

Calculate:

• Number of cans along the internal length
• Number of cans along the internal width
• Number of layers allowed by the internal height

Round each result down to a whole number, then multiply them together.

Estimated can count = cans along length × cans along width × number of layers

Calculation Example

Assume the buyer has selected a reference can measuring:

• Diameter: 66 mm
• Height: 122 mm

The cooler’s usable internal dimensions are:

• Length: 350 mm
• Width: 220 mm
• Height: 250 mm

The estimate is:

• Length: 350 ÷ 66 = 5 whole cans
• Width: 220 ÷ 66 = 3 whole cans
• Height: 250 ÷ 122 = 2 layers

Estimated capacity:

5 × 3 × 2 = 30 cans without ice

This is only an early estimate. The actual number may be lower because of rounded corners, seams, wall movement, and the size of the zipper opening. A staggered packing arrangement may also produce a different result.

Always check the final claim with a finished sample.

7. State Whether Ice Is Included

A can-capacity claim is incomplete unless it explains whether cooling material is included.

There are three common ways to describe capacity.

Cans Without Ice

This gives the highest can count but does not represent how everyone will use the cooler.

Example:

Holds up to ___ × 355 mL cans without ice.

Cans With Loose Ice

This is more realistic for coolers designed to hold loose ice, but the test must define:

• Number of cans
• Weight or volume of ice
• Type of ice
• Packing order
• Whether the bag must close normally

Example:

Holds ___ × 355 mL cans with ___ kg of cubed ice.

Cans With Ice Packs

This may be more suitable for ordinary sewn cooler bags that are not designed to contain melted ice.

The specification should state:

• Number of ice packs
• Dimensions of each ice pack
• Position of the ice packs
• Number and size of cans

Example:

Holds ___ × 330 mL cans with two ice packs measuring ___ × ___ × ___ mm.

Use the same packing method when comparing different samples. Otherwise, the results will not be comparable.

8. Verify Capacity With a Finished Sample

Calculations are useful during design, but a physical packing test is more reliable before production.

Use the following process:

1. Confirm the exact can size.
2. Decide whether the test includes ice or ice packs.
3. Place the finished cooler in its normal shape.
4. Pack the cans in the agreed direction.
5. Add the specified cooling material.
6. Close the zipper or lid completely.
7. Check whether the bag is distorted or overfilled.
8. Count the cans and photograph the packing arrangement.
9. Repeat the test if the result is close to the claimed limit.

Do not force the zipper closed or stretch the bag to add one more can. The cooler should close normally and remain practical to carry.

For a sewn cooler bag, check whether overpacking puts too much pressure on the lining, seams, or zipper.

For an RF-welded waterproof cooler, check whether overpacking puts excessive stress on the airtight zipper or welded seams.

9. Check the Opening, Not Just the Interior

A cooler may have enough space inside but still be difficult to pack because the opening is too small.

This is especially important for:

• Cooler backpacks
• Tall tote coolers
• Roll-top coolers
• Coolers with stiff airtight zippers
• Bags with thick foam around the lid
• Designs with inward-folding zipper panels

During sample review, check:

• Clear zipper-opening length
• Clear opening width
• Whether cans can pass through easily
• Whether the lid stays open during packing
• Whether users can remove items from the bottom
• Whether the zipper can close without pressing against the contents

A large calculated volume has limited value if users cannot easily load and unload the cooler.

10. Capacity Also Affects Carrying Weight

More capacity is not always better. A larger cooler can become uncomfortable or unsuitable for one person to carry when fully loaded.

When deciding the size, also consider:

• Total weight of the drinks
• Weight of ice or ice packs
• Empty weight of the cooler
• Handle and shoulder-strap strength
• Strap width and padding
• Whether one or two people will carry the bag
• Expected carrying distance

Once the intended contents are known, the manufacturer can use the actual packed weight to set the handle and strap test load.

Our guide to testing cooler bag handles and straps under load explains how to check the complete carrying system before bulk production.

11. Write the Capacity Clearly in the RFQ

Instead of requesting only “a 20-liter cooler bag,” give the supplier enough information to understand the intended use.

A useful RFQ should include:

• Target internal capacity in liters
• Maximum external dimensions
• Required insulation thickness
• Reference can size
• Required number of cans
• Whether the can count includes ice
• Type and amount of cooling material
• Preferred can orientation
• Required compartments or dividers
• Required zipper or opening size
• Expected total carrying weight
• Method used to verify the capacity

This helps the supplier balance internal space, insulation, external size, and carrying comfort.

A thicker insulation layer may improve cold retention, but it can also reduce internal space or increase the outside dimensions. These trade-offs should be discussed during product development rather than after the sample is finished.

These details can also be added to your custom cooler bag RFQ checklist before sample development begins.

12. Use Clear Capacity Claims on Product Pages and Packaging

Do not combine liters and can count unless both figures have been checked.

A clear capacity statement might follow this format:

Internal capacity: approximately ___ L, measured from the finished main compartment. Fits up to ___ × ___ mL cans without ice, or ___ cans with the specified ice packs.

Also record:

• Sample version used for the test
• Internal measurement method
• Reference can dimensions
• Packing direction
• Ice or ice-pack conditions
• Whether the bag closed normally

Avoid vague claims such as:

• Large capacity
• Holds a full day of drinks
• Fits 30 cans
• 20-liter exterior size

“Fits 30 cans” is unclear unless the can size and ice conditions are stated. “20-liter exterior size” is also incorrect because liters describe volume, not external length, width, and height.

Cooler Bag Capacity Specification Template

The following template can be added to an RFQ, sample approval sheet, or product specification.

Product Information

• Product name:
• Style number:
• Target market:
• Cooler type:
• Sewn insulated cooler bag
• RF-welded waterproof cooler
• Other:

Capacity Requirements

• Target internal capacity:
• Unit:
• Liters
• US quarts
• Maximum external dimensions:
• Required insulation thickness:
• Usable opening size:

Reference Can

• Can volume:
• Can diameter:
• Can height:
• Packing direction:
• Upright
• Horizontal
• Mixed

Packing Conditions

• Required can count:
• Without ice
• With loose ice
• With ice packs
• Ice weight or volume:
• Ice-pack quantity:
• Ice-pack dimensions:
• Bag must close normally:
• Yes
• No

Verification

• Internal dimensions measured:
• Calculated internal volume:
• Actual can count:
• Finished-sample version:
• Packing photographs required:
• Maximum packed weight:
• Approved by:
• Approval date:

Conclusion

Calculating cooler bag capacity starts with the internal dimensions:

Internal length × internal width × internal height ÷ 1,000 = liters

However, this result is only an estimate of the internal volume. It does not automatically show how many cans will fit.

A reliable can-capacity claim must define the can size, packing direction, and whether ice or ice packs are included. The final result should then be checked with a finished sample that closes normally without being stretched or distorted.

For OEM buyers, the clearest approach is to include both figures in the product specification:

• Internal capacity in liters
• Verified can capacity under defined packing conditions

This avoids misleading product claims and helps the manufacturer balance capacity, insulation thickness, external size, and carrying weight.

Develop the Right Cooler Bag Size With Vancharli Outdoor

Vancharli Outdoor supports OEM and ODM development for conventional sewn cooler bags and RF-welded waterproof coolers. Buyers can define the target capacity, external dimensions, insulation, can size, cooling method, and carrying requirements during the sampling stage.

Explore our custom cooler bag manufacturing options or view our RF-welded waterproof cooler bag solutions.

Frequently Asked Questions