Both quotes below came back on 2026-08-22 for the exact boxes and lane described.
Two seats, one lane, five services apiece
We ran a convertible car seat in its original retail box and an infant car seat with its base in its original box from Berkeley Heights, NJ 07922 to Denver, CO 80202 on 2026-08-22. Here is every rate that came back, cheapest first.
Convertible seat, boxed
25 × 20 × 22 in
22 lb packed
Infant seat with base, boxed
24 × 19 × 18 in
14 lb packed
Route
Berkeley Heights, NJ 07922
to Denver, CO 80202
A cross-country lane. A shorter one prices every row below it.
| Seat | Carrier | Service | Price | Estimated transit |
|---|---|---|---|---|
| Infant + base | UPS | Ground | $71.42 | 4-5 business days |
| Infant + base | FedEx | Ground Economy | $83.88 | 5-6 business days |
| Infant + base | UPS | Ground Saver | $94.81 | about 6 business days |
| Convertible | UPS | Ground | $100.81 | 4-5 business days |
| Convertible | UPS | Ground Saver | $103.35 | about 6 business days |
| Infant + base | FedEx | Ground | $104.43 | 4-5 business days |
| Convertible | FedEx | Ground Economy | $124.71 | 5-6 business days |
| Infant + base | UPS | 3 Day Select | $126.49 | 3-4 business days |
| Convertible | UPS | 3 Day Select | $178.12 | 3-4 business days |
| Convertible | FedEx | Ground | $184.35 | 4-5 business days |
The two cheapest rows are UPS Ground on both seats, and they land almost thirty dollars apart for two seats that differ by only 8 lb on the scale. What separates them is the carton: 11,000 cubic inches against 8,208. Carriers price the box a seat forces you into, not the seat riding inside it.
Why the bigger box costs more than the seat inside it
Dimensional weight bites first
Every carrier compares the scale reading against a size-based number and bills whichever is higher. A convertible seat's box is rarely the heavy part of the equation.
A cubic-inch line that matters
UPS's own published threshold for its Additional Handling charge is 10,368 cubic inches (ups.com, read 2026-08-22). The convertible box above, at 25 × 20 × 22 in, comes to 11,000 — past it. The infant seat's box, at 24 × 19 × 18 in, comes to 8,208, under it.
USPS has its own ceiling
USPS caps Ground Advantage at 70 lb of scale weight and 130 in of combined length and girth (usps.com, read 2026-08-22). Both boxes above land under that 130-inch line on paper, at 109 in and 98 in, though USPS did not turn up among the rates returned for either lane here — worth a check on your own ZIP pair.
Common questions
How much does it cost to ship a car seat?
$71.42 to $184.35 in the boxes quoted on this page: $71.42 for an infant seat with its base, $100.81 to $184.35 for a bulkier convertible seat, both from Berkeley Heights, NJ to Denver, CO on 2026-08-22. A shorter zone or a tighter box moves the number down from there.
Why did the convertible seat cost so much more than the infant seat?
Mostly the box, not the seat. The convertible carton in this example came to 11,000 cubic inches against 8,208 for the infant seat's box, and every carrier bills a large box as if it weighed more than the scale says, no matter how light the seat inside actually is.
Is this the kind of car seat that stays bolted to a vehicle?
No. This page prices the child seats parents carry between cars — infant, convertible and booster. A vehicle's own upholstered seat is a different item with a different weight and box, covered on its own page.
Does a boxed car seat run into a large-package surcharge?
It depends on the box, and it is worth checking before you tape one shut. UPS publishes 10,368 cubic inches as the line where its Additional Handling charge applies, and a full-size convertible seat's factory carton can sit right on top of that number.
Should I ship the seat in its original box?
Yes whenever you still have it. The molded foam inserts hold the seat away from the cardboard on every side, which is exactly what a reused moving box or a taped-together assembly of two smaller boxes struggles to do.