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Package Size Checker

Understand your parcel dimensions and weight, compare two packaging options, and see what is worth changing.

Your package at a glance

Illustrative dimensions · Enter all three dimensions to see your package

Measure the outside of the packed parcel. Include the box and cushioning in its weight.

Enter package details

Option A · Current packaging

The factor uses the current units. 139 is an initial reference; use the factor for your service. Switching units converts both measurements and the factor.

Understand dimensions and weight

Enter dimensions, weight and a factor to check your package, or load an example below.

Reference billable weight is the higher of actual and DIM weight. Service rounding, DIM eligibility and surcharges are not applied. This page does not determine carrier acceptance.

Compare another packaging option

Use the same units and factor to see how another box changes volume and reference billable weight. Option B is optional and does not affect the single-package check.

Option B · Alternative packaging

Enter option B to compare. Both options use the units and DIM factor selected above.

Less volume does not guarantee a lower rate. The comparison does not verify that the contents fit or that cushioning and protection are sufficient.

Start with a shipping scenario

These are illustrative examples, not carrier rules. Loading one replaces option A and clears option B for a fresh comparison.

Light and bulky

18 × 14 × 12 in · 2 lb

When DIM weight exceeds actual weight, compare a more compact package.

Small and dense

8 × 6 × 4 in · 8 lb

A smaller box may still leave actual weight as the reference billable weight.

Long parcels

36 × 6 × 6 in · 4 lb

Check the longest side and length plus girth as well as volume.

Flat parcels

16 × 12 × 2 in · 2 lb

Even a thin parcel has volume. Measure its maximum packed thickness.

How to measure and adjust packaging

Longest side Girth
Girth = 2 × (sum of the other two sides)

01 · Measure the packed parcel

Pack first, then measure the outermost length, width and height. Weigh the parcel with all packaging materials.

02 · Separate girth from length plus girth

The tool identifies the longest side. Girth is twice the sum of the remaining sides; length plus girth adds the longest side. Input order does not change these results.

03 · Compare without compromising protection

Copy the current package, then enter a feasible alternative size and packed weight. Check cushioning, strength and closure before comparing results.

Measure a soft mailer at its maximum dimensions after filling and sealing it. A bounding box can illustrate space for tubes or irregular parcels, but this tool’s girth and volume formulas apply to rectangular packages, not service-specific irregular-shape rules.

Measurement reference: USPS package preparation and measuring guidance ↗

Frequently asked questions

Does this tool return final carrier billing?

No. It compares actual and DIM weight using your factor, without service eligibility, rounding or surcharges. Final charges depend on the service rules and invoice.

Is DIM weight always higher than actual weight?

No. DIM weight depends on dimensions and the factor. Small, dense parcels may be driven by actual weight. The result shows the difference.

What should I do if risk is detected?

If DIM weight is much higher than actual weight, compare a more suitable package. For a large longest side or length plus girth, check the specific service limits before comparing rates.

Should I enter product dimensions or box dimensions?

Enter the outside dimensions and total weight after packing. Internal box dimensions, empty mailer dimensions and unpacked product dimensions are not substitutes.

How does girth differ from length plus girth?

For a rectangular parcel, length is the longest side. Girth is twice the sum of the other two sides. Length plus girth adds the longest side to that girth.

Why does the DIM factor change with the units?

The factor is in in³/lb or cm³/kg. It must convert with dimensions and weight to preserve the same calculation. 139 and 5000 are not exactly equivalent; switching back restores the original inputs.

Does 20% less package volume mean 20% lower postage?

Not necessarily. Actual weight, rate tiers, zones and surcharges affect the charge. This tool compares volume and weight metrics, not monetary savings or whether the contents fit.

Can I use it for mailers, tubes or irregular parcels?

Measure a filled and sealed mailer at its maximum dimensions. For tubes and irregular parcels, the bounding box illustrates occupied space, but actual volume, girth and carrier billing rules need separate checks.