Does USPS Charge By Weight Or Size? (Your Full Guide)

Shipping a package has never been easier, with options from UPS, FedEx, and yes, the United States Postal Service, or USPS.

But have you ever brought your package to the post office, had them price it for you, and found yourself surprised by the cost (in a good or a bad way)?

You might have wondered: Does USPS charge by weight or size? How did they arrive at that price? Here is what you need to know.

Does USPS Charge By Weight Or Size?

The United States Postal Service most commonly charges based on weight and distance, as with First-Class mail and Priority Express. However, some services may apply dimensional weight pricing if the parcel exceeds size limits. Dimensional weight pricing factors in length, height, and width. Some services offer convenient flat-rate shipping for parcels up to 70 lbs.

Sound a little confusing? I can break down for you how much USPS charges per pound for different services, whether it’s cheaper to ship UPS or USPS, and whether or not it’s cheaper to use your own box when shipping. Keep reading for all those details!

How Much Does USPS Shipping Cost Per Pound?

The per-pound price to ship a parcel depends on the type of USPS shipping service you select and the distance your item will be covering.

You can ship parcels via First-Class Package Service-Retail, Retail Ground, Priority Mail, and Priority Mail Express.

Four of these may ship by dimensional weight (DIM) if the size maximum has been exceeded. USPS calculates DIM by Length x Width x Height ÷ 166.

Here are the types of parcel shipping services, each broken down with the price-per-pound range given, as well as any Flat-Rate services or DIM pricing.

First-Class Package Service-Retail

  • First-Class Package Service is for smaller packages, less than 13 oz.
  • Packages generally take between 1 and 3 business days
  • Prices start at $4 for 1 oz., rising to $6.25 for 13 oz.

Retail Ground

  • This service includes USPS tracking and is a good alternative when packages are too large for Priority Mail and Priority Express
  • Limits to Retail Ground include 70 lbs. of weight and 130 inches in combined length and girth
  • Prices start at $7.70 for one pound and climb to $49 for 70 lbs.
  • DIM pricing may be applied if the parcel exceeds the size limit.

Priority Mail

  • This service is the “next step up” from First Class shipping
  • It is slightly faster (1-3 business days), can deliver on Sundays (for an additional fee), and includes shipping of letters, large envelopes, and parcels
  • Parcels must be 70 lbs. or less, with a max 108 inches in combined length and girth
  • Prices start at $7.70 for one pound, all the way up to $49 for 70 lbs.
  • This service also includes Flat Rate shipping, which starts at $7.95 for envelopes, $8.45 for small boxes, $15.50 for medium and $21.90 for large
  • DIM pricing may be applied if the parcel exceeds the size limit.

Priority Mail Express

  • This service is the fastest and includes next-day and 2-day shipping on letters, envelopes, and parcels
  • Parcels must be 70 lbs. or less, with a combined length and girth of 108 inches max
  • Prices start at $26.35 for a half-pound and climb to $184.30 for 70 lbs.
  • Priority Express also offers flat-rate envelopes, which range from $22.75 to $23.25
  • DIM pricing may be applied if the parcel exceeds the size limit.

Parcel Select

  • This service is for regular shippers who don’t need to get their parcels anywhere in a hurry and who want the cheapest shipping rates
  • Weight limit is 70 lbs. and size limit is 108 inches in length and girth combined
  • Prices start at just $3.30 for one pound; the price for a 70-lb. package starts at only $9.24!
  • DIM pricing may be applied if the parcel exceeds the size limit.

Ultimately, the best way to calculate your shipping costs beforehand is to use’s handy shipping calculator tool here.

Is It Cheaper To Send a Box Via UPS Or USPS?

Is It Cheaper To Send A Box UPS Or USPS?

When it comes to low prices for parcel shipping, it’s hard to beat USPS.

That applies to shipping competitor UPS, which is generally priced higher (sometimes much higher) than your government-run Postal Service for basic parcel shipping.

Additionally, USPS’s flat-rate shipping options are difficult to beat. With a weight limit of 70 lbs., you can ship a lot of things in one of their flat-rate boxes and save a ton of money.

That said, however, you may be forced to spend the extra cash on UPS or FedEx shipping if your item is very heavy.

USPS cannot ship anything over 70 lbs., so if your item exceeds that weight, you will have to turn to one of their competitors.

Is It Cheaper To Ship USPS With Your Own Box?

Whether or not it’s cheaper to ship USPS with your own box depends on the weight of your item.

For example, if you are shipping something heavier, say, 60 lbs., and it will fit inside a USPS Priority Mail Flat-Rate box, that is your cheapest option.

The box is free (you can pick one up in any post office lobby), and the flat rate for a large box is $21.90.

Shipping a 60-lb. item in your own box starts at $42.90 and could go up to $277.15, depending on how far you’re shipping it.

Can I Use My Own Box For the USPS Flat Rate?

You cannot use your own box for USPS’s flat rate shipping options, such as Priority Flat Rate and Priority Express Flat Rate.

Instead, you must use the USPS-approved boxes, which come in three different sizes (as well as a few different envelope options).

To learn more about Priority flat rate boxes, you can visit this page here (Priority Express only offers flat rate envelopes at this time, which you can find the prices for here).

You can use your own box for any shipping service other than USPS’s flat rate shipping services, however.

To know more about USPS, you can also read our posts on whether or not USPS scans packages, if USPS updates tracking, and if USPS charges for change of address.

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Marques Thomas

Marques Thomas graduated with a MBA in 2011. Since then, Marques has worked in the retail and consumer service industry as a manager, advisor, and marketer. Marques is also the head writer and founder of

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