USPS Shipping Rates

How USPS Determines a Shipping Rate

Three major factors make up that calculated USPS shipping rate — the weight of an order, the distance it must travel to reach the customer’s door, and the shipping method you select.

1. A Package’s Weight (Actual and Dimensional)

Weight is straightforward… for the most part. How much a package actually weighs — the number that pops up on your scale after you weigh it — is the primary means of determining order weight. But there is an exception.

Sometimes USPS (and other shipping carriers) will work with what’s known as “dimensional weight” to calculate a shipping rate. Long story short, it’s a way of figuring out how much space a package will take up, rather than just how much it weighs. Here’s how they go about determining it.

Dimensional Weight = (Length x Width x Height) / 166

You might recognize the first part of that equation from middle school — it’s the volume of your package! USPS then divides it by their divisor (166), a digit that brings said volume down to a reasonable number that’s comparable to the actual weight of the order. Other shipping carriers may have different divisors; 166 is another common one.

At the end of the day when it’s shipping time, USPS chooses whichever weight is greater and uses it to determine your shipping rate.

Dig into deeper detail on the ins and outs of weighting by reading our Shipping Rate Guide.

2. Distance Travelled (Zones)

The distance your order needs to travel is definitely going to play a role in your USPS shipping rate. Like other carriers, USPS utilizes what are called zones to segment distances, and they have a total of 8 of ‘em.

Think of zones as waves that fan out from the shipment’s origin location. The further the package is travelling to, the higher the zone number. Whichever zone your ship-to address slots into will be the foundation of your rate, and the higher the zone, the higher the final price.

3. USPS Shipping Methods

Cheap or expensive, fast or slow, USPS offers an array of shipping methods for you to choose from. And, as you’d expect, the method you select will greatly affect your shipping rate.

First-Class Mail

First Class is the top dog when it comes to cost-effectiveness. It’s a very cheap method — but only if your shipment is lightweight. First Class deals exclusively with orders weighing less than 15.99 ounces, and delivery is guaranteed within 1 - 3 days at a low cost.

As of 2019, pricing for First-Class Mail is also zone-based. Below are the current rates by zone and weight.

Weight of First-Class Package	COST PER ZONE
	Zones 1 and 2	Zone 3	Zone 4	Zone 5	Zone 6	Zone 7	Zones 8 and 9
1–4 oz	$2.66	$2.68	$2.70	$2.76	$2.84	$2.96	$3.09
5–8 oz	$3.18	$3.20	$3.22	$3.28	$3.36	$3.49	$3.63
9–12 oz	$3.82	$3.85	$3.88	$3.96	$4.06	$4.19	$4.33
13–15.99 oz	$4.94	$4.98	$5.02	$5.12	$5.24	$5.38	$5.53

Priority Mail

If a shipment tops a pound in weight, you’re going to be using Priority Mail, a standard group of USPS shipping methods. Unlike First Class — where you can package how you please — USPS includes the packaging for all Priority Mail shipments free of charge. If it fits in the box, it ships within one to three days or overnight through its Express option (in urban areas).

Priority Mail Flat Rate

Flat rate is exactly that — flat. Priority Mail Flat Rate contains an assortment of packaging options, from envelopes to large boxes, that get charged a single rate, regardless of where the order’s headed. The smaller the packaging type, the cheaper the rate, and as long as the items inside the order don’t exceed weight and dimension limits, it ships.

Priority Mail Regional Box

A variation of Priority Mail that’s only available online, Regional Boxes come in two flavors — Box A and Box B — that differ only in size. Compared to Flat Rate, Regional Box rates are fixed by weight (up to 20 pounds) but vary by distance; you will be charged by the zone.

For further info on all of USPS’ offerings, from additional services to USPS package dimensions and other shipping options, take a look at our USPS Guide.

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USPS Pricing Tiers

But wait — there’s always more. USPS has a unique way of pricing; it uses three tiers to ultimately decide your final shipping rate.

Retail

Retail pricing is where the most expensive rates are going to be, mostly because they won’t be discounted. Retail rates are what you get over-the-counter through a USPS post office.

Commercial Base

Commercial Base rates are where the discounts come in. They’re available through websites like usps.com and some USPS-approved third party providers.

Commercial Plus

Commercial Plus rates are what you get through Ordoro. Think of them as Commercial Base rates on steroids — they’re the most heavily discounted rates available. USPS reserves these exclusively for a limited set of high-volume partners like yours truly!

Read our USPS Shipping Rate FAQ for more on how we work with USPS.