How do I calculate void fill for a box?

Subtract the product’s volume from the box’s inside volume, then multiply by the share of that space you fill.

How do I work out void fill cost per order?

Multiply the fill volume by the material’s price per unit of volume, such as per cubic foot or per liter.

What if my fill is priced per bag?

Divide the bag price by the volume it holds. An $18 bag holding 20 ft³ is $0.90 per cubic foot.

Should I fill 100% of the empty space?

Use 100% as a starting point, then lower it if the pack leaves space empty or the material doesn’t fill corners.

Does a smaller box save on void fill?

Usually, because it leaves less empty space around the product.

Illustration of an open box with a product inside and the empty space around it shaded for void fill

Shipping & packaging

How to Estimate Void Fill Cost per Package

Void fill is one of the smaller costs on a packing line, but it repeats on every order. A per-package estimate turns a bag or roll price into a cost you can compare between box sizes, materials, and suppliers.

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Step 1: find the empty space

Work out the box’s inside volume and subtract the product’s. A 14 × 10 × 6 in box holds 840 in³; an 8 × 6 × 3 in product takes 144 in³, leaving 696 in³ — about 0.4028 ft³.

Step 2: decide how much of it to fill

Not every pack fills every gap. If some space stays empty by design, or the material leaves gaps, use a share less than 100%. Two 6 × 4 × 4 in products in a 12 × 12 × 8 in box leave 960 in³; filling 75% of it is 720 in³.

Step 3: put the price per volume

Divide a bag or box of material by the volume it holds to get a price per cubic foot, liter, or cubic meter, then multiply by the fill volume.

Step 3: put the price per volume comparison
Box and product	Fill	Price	Cost per package
14 × 10 × 6 in, one 8 × 6 × 3 in item	0.4028 ft³ (100%)	$0.40 per ft³	$0.16
14 × 10 × 6 in, one 8 × 6 × 3 in item	0.4028 ft³ (100%)	$0.90 per ft³	$0.36
12 × 12 × 8 in, two 6 × 4 × 4 in items	0.4167 ft³ (75%)	$0.90 per ft³	$0.38

At $0.40 per cubic foot, the first pack costs about $161.11 in fill over 1,000 orders.

Making the estimate realistic

Test a real pack: weigh or count the fill used and compare.
Adjust the fill share until the estimate matches what you see.
Recheck when you change box sizes — a better-fitting box cuts fill as well as dimensional weight.

Void Fill Cost per Package FAQ

How do I calculate void fill for a box?: Subtract the product’s volume from the box’s inside volume, then multiply by the share of that space you fill.
How do I work out void fill cost per order?: Multiply the fill volume by the material’s price per unit of volume, such as per cubic foot or per liter.
What if my fill is priced per bag?: Divide the bag price by the volume it holds. An $18 bag holding 20 ft³ is $0.90 per cubic foot.
Should I fill 100% of the empty space?: Use 100% as a starting point, then lower it if the pack leaves space empty or the material doesn’t fill corners.
Does a smaller box save on void fill?: Usually, because it leaves less empty space around the product.