How to measure a parcel, read carrier size limits and avoid oversize surcharges

Carriers set their size rules around one number, length plus girth, and a box that is a couple of inches over a threshold can pick up a surcharge bigger than the postage itself. This guide shows how to take the measurement, what the thresholds are for USPS, UPS, FedEx and DHL Express as of 2026, and how to keep a shipment on the right side of them.

How to measure a box the way the carrier does

Measure the outside of the packed carton along its three edges, after it is taped shut. If a side bulges, measure the bulge, because the sorting hub’s scanner will.

Length is always the longest of the three sides, whatever the box’s printed orientation says. The other two sides form the girth: wrap a tape once around the box across the two smaller faces, or simply calculate it.

Girth = 2 × (width + height), using the two shorter sides

Length plus girth = longest side + girth

For a 24 × 18 × 12 in carton, the girth is 2 × (18 + 12) = 60 in and length plus girth is 24 + 60 = 84 in. The parcel size checker sorts the three sides for you, so you can type them in any order and get the same answer the carrier will.

What the length plus girth rule is for

Automated sorters, conveyors and delivery vans are built around a certain envelope of parcel sizes. A long, thin box jams belts and needs a person to carry it; a huge cube takes the space of several ordinary parcels. Rather than measure every awkward shape individually, carriers define one or two thresholds on length plus girth, plus a few on the individual sides and the weight, and price anything beyond them steeply. Below the first threshold you pay the standard rate. Between the first and second you still ship but with a surcharge. Above the top figure the parcel is refused or has to move as freight.

Carrier limits and surcharge names

The figures below are the published retail limits for standard domestic services (USPS, UPS, FedEx) and standard DHL Express international pieces, and they are the same figures the checker uses. Thresholds and fee amounts change, and contracted accounts differ, so confirm the exact charge on the carrier’s current rate card before you commit to a carton.

Carrier	Maximum length	Maximum length plus girth	Maximum weight	Surcharge thresholds
USPS Ground Advantage / Priority Mail	–	130 in	70 lb	Large Package surcharge above 108 in length plus girth
UPS Ground / Air	108 in	165 in	150 lb	Large Package surcharge above 96 in length or 130 in length plus girth; Additional Handling above 48 in length, 30 in second side, or 50 lb
FedEx Ground / Home Delivery	108 in	165 in	150 lb	Oversize charge above 96 in length or 130 in length plus girth; Additional Handling above 48 in length, 30 in second side, or 50 lb
DHL Express (international, per piece)	120 cm	–	70 kg	No length plus girth figure; each piece must fit 120 × 80 × 80 cm

Three points are worth reading twice. USPS has no separate length limit but the tightest length plus girth figures, 108 in for the surcharge and 130 in as a hard stop. UPS and FedEx share identical thresholds but different names: UPS calls its size fee the Large Package surcharge, FedEx calls it the Oversize charge, and both add Additional Handling for parcels that are merely awkward rather than huge. DHL Express works on per-side maximums in centimetres rather than on girth, so a box can pass every US rule and still be too long for a DHL piece.

In metric terms, 48 in is about 122 cm, 108 in is 274 cm, 130 in is 330 cm and 165 in is 419 cm. The 50 lb Additional Handling weight is about 22.7 kg, and the 150 lb ceiling is about 68 kg.

Two worked examples

First, a 40 × 30 × 30 cm carton, a common size for a medium order.

1. Longest side: 40 cm, so length is 40 cm (15.7 in).
2. Girth: 2 × (30 + 30) = 120 cm (47.2 in).
3. Length plus girth: 40 + 120 = 160 cm, which is 63.0 in.
4. Against the limits: 63 in is far below the 108 in USPS surcharge line, and 15.7 in is nowhere near 48 in. Every side is under DHL’s 120 × 80 × 80 cm. No surcharge with any of the four carriers.

Second, a 30 × 20 × 15 in carton, roughly 76 × 51 × 38 cm.

1. Longest side: 30 in.
2. Girth: 2 × (20 + 15) = 70 in.
3. Length plus girth: 30 + 70 = 100 in (254 cm).
4. Against the limits: 100 in is under USPS’s 108 in and well under the 130 in UPS and FedEx surcharge line. The 30 in length is under 48 in, and the 20 in second side is under 30 in. For DHL, 76 cm is under 120 cm and 51 cm and 38 cm are under 80 cm. It fits everywhere with no size surcharge, but only if it weighs 50 lb or less; heavier than that and UPS and FedEx add Additional Handling on weight alone.

Now stretch the second box. A 54 × 16 × 14 in carton holds about the same volume as a 30 × 24 × 17 in one, but its girth is 2 × (16 + 14) = 60 in and length plus girth is 114 in. USPS now charges the Large Package surcharge because 114 exceeds 108, and UPS and FedEx add Additional Handling because 54 in is longer than 48 in. Same contents, two fees, purely because of the shape.

Box	Length	Girth	Length plus girth	Result
40 × 30 × 30 cm	15.7 in	47.2 in	63.0 in	Fits all four carriers
30 × 20 × 15 in	30 in	70 in	100 in	Fits all four carriers
54 × 16 × 14 in	54 in	60 in	114 in	USPS Large Package; UPS and FedEx Additional Handling

Staying under a threshold

Shape matters more than volume. For a fixed volume, a cube minimizes length plus girth, and a long thin box maximizes it, so when you have a choice, choose the squatter carton. If a product is inherently long, such as a curtain rod or a rolled rug, check the 48 in line first, because that is the one long items hit before anything else.

Measure before you buy a pallet of cartons. Supplier catalogues list internal dimensions; the carrier measures external ones, and corrugated board adds roughly 0.5 in to each dimension on a single-wall box. A carton sold as 47 in long can measure 48.25 in packed.

Split or combine deliberately. Two parcels under every threshold are frequently cheaper than one that carries a surcharge. But each parcel has its own base charge and its own dimensional weight, so run both options through the volumetric weight calculator and compare the totals rather than assuming.

Watch the weight rules as well as the size rules. A compact 52 lb box triggers Additional Handling at UPS and FedEx even though its dimensions are modest, and USPS stops at 70 lb regardless of size.

Keep a short list of your five or six standard cartons with their length plus girth already calculated. Most surcharge surprises come from a one-off box grabbed from the storeroom rather than from the cartons you use every day.

Quick checklist

• Measure the packed box, outside edges, including any bulge.
• Length is the longest side; girth is twice the sum of the other two.
• USPS: surcharge above 108 in, refused above 130 in length plus girth, 70 lb maximum.
• UPS and FedEx: Additional Handling above 48 in, 30 in second side or 50 lb; size surcharge above 96 in length or 130 in length plus girth; hard stops at 108 in, 165 in and 150 lb.
• DHL Express: each piece within 120 × 80 × 80 cm and 70 kg.
• Confirm the current fee on the carrier’s rate card before shipping in volume.