Linear Inches Calculator (luggage L + W + H and USPS length + girth)

Understanding the linear inches calculator — concept and principle

This calculator adds up the length, width and height of a bag or box to give its linear size in inches and centimetres, checks it against an airline limit, and also works out length plus girth for US postal parcel limits. Use it before flying with checked or carry-on bags, or before posting a large parcel.

Add the three sides: with the default inputs the result is 62 in = fits (≈ 157 cm, 0 in to spare).

How it is calculated

Linear size = length + width + height (cm ÷ 2.54 for inches).
Room left = limit − linear size; negative means too big.
Length + girth = longest side + 2 × (sum of the other two sides).
USPS checks: 108 in general parcel limit; 130 in for USPS Ground Advantage.

The principle

Airlines limit baggage by the sum of its three dimensions because it is simple to measure and roughly tracks the space a bag takes in the hold. Postal services use a different measure: the longest side plus the girth, the distance around the thickest part at right angles to it. Girth is twice the sum of the two shorter sides, so a long thin parcel and a cube of the same linear size can differ a lot in length plus girth. Measure bags including wheels and handles, because the airline will.

Worked example

Default inputs: 30 × 20 × 12 in, limit 62 in.

Linear size = 30 + 20 + 12 = 62 in = 62 × 2.54 = 157.5 cm, shown as 157 cm.
62 ≤ 62: Fits the limit; room left = 0 in.
Length + girth = 30 + 2 × (20 + 12) = 94 in.
94 ≤ 108: Within the limit for the USPS general limit and within the 130 in Ground Advantage limit.

Each point is the calculator re-run with only “Length” changed; the gold point is the default example. Change the inputs above and this chart follows your numbers.

Length	Linear size (in)
7.5	39.5
15	47
22.5	54.5
30	62
37.5	69.5
45	77
60	92

How to read the result

A result exactly at the limit leaves no margin; a bulging bag can easily measure more at the check-in desk. Many airlines use 62 linear inches (158 cm) for checked bags, but carry-on limits are smaller and often given as separate maximum dimensions, so check each one. Weight limits apply separately.

Common mistakes

Measuring without wheels and handles.
Using linear inches for postal limits, which use length plus girth.
Assuming every airline uses the same limit.
Measuring a soft bag when it is empty rather than packed.

Keep in mind: Airline and postal rules change and differ by route and service. Check the current rules with your carrier before travelling or shipping.

Frequently asked questions

What are 62 linear inches?

The sum of length, width and height is 62 inches (about 158 cm), a common checked-bag limit.

How do I measure girth for USPS?

Measure around the thickest part at right angles to the longest side, which is twice the sum of the other two sides.

Do wheels and handles count?

Yes. Airlines measure the bag including wheels and handles.

Sources: USPS Postal Explorer, Quick Service Guide 201e (length and girth, 108 in and 130 in limits) · NIST Special Publication 811 (2008), Appendix B (1 in = 2.54 cm)

Checked 9 Nov 2026. USPS Postal Explorer, Quick Service Guide 201e (length = longest dimension; girth = distance around the thickest part; 108 in general maximum, 130 in for USPS Ground Advantage). Airline limits vary — the 62 in default is an example value.

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