Does USPS charge by weight or size?

Both. For most standard packages, weight is the primary factor. However, for large, lightweight packages (over 1 cubic foot), USPS uses Dimensional Weight, which charges you based on the volume of the box rather than its actual weight.

What is the cheapest way to ship a package?

For packages under 1 lb, USPS Ground Advantage is almost always the cheapest option. For packages over 1 lb, it depends on the distance. Ground Advantage is usually cheapest for nearby zones, while Flat Rate Priority Mail can be cheaper for heavy items going to Zone 8.

How do I know which Zone I am shipping to?

Zones are determined by the distance between your zip code and the recipient's zip code. You can look up the exact zone using the USPS Domestic Zone Chart.

Is insurance included in USPS rates?

Yes, both Ground Advantage and Priority Mail include $100 of insurance coverage for free. Priority Mail Express includes up to $100 as well. Additional insurance can be purchased for higher-value items.

Can I use my own box for Priority Mail?

Yes, you can use your own box for 'Weight-Based' Priority Mail. However, you cannot use your own box for 'Flat Rate' pricing; you must use the specific Flat Rate branded boxes provided by USPS for free.

USPS Rate Calculator - Estimate Postage & Shipping Costs

How to Calculate USPS Postage Rates

Calculating postage with the United States Postal Service (USPS) can seem complicated due to the variety of services, weight classes, and destination zones. However, using a USPS Rate Calculator and understanding the basic factors that influence the price can help you estimate your shipping costs accurately and find the most economical option for your package.

The three main factors that determine your USPS shipping rate are:

Weight and Dimensions: Heavier and larger packages cost more. USPS rounds up to the nearest pound for most services (e.g., 1.1 lbs is charged as 2 lbs).
Distance (Zone): The farther the package travels, the higher the cost. USPS divides the US into 9 zones based on the distance from the origin zip code.
Service Speed: Faster delivery services like Priority Mail Express cost significantly more than standard Ground Advantage.

Understanding USPS Services

USPS offers several service levels tailored to different needs. Choosing the right one is the easiest way to save money.

1. USPS Ground Advantage™

Replaced "First Class Package" and "Retail Ground" in 2023. This is the most affordable option for packages up to 70 lbs.

Best For: Non-urgent packages, lightweight items (under 1 lb), and cost-conscious shipping.
Delivery Time: 2-5 business days.
Tracking: Included.
Insurance: $100 included.

2. Priority Mail®

The standard for fast, reliable shipping. It offers a good balance of speed and price.

Best For: Time-sensitive shipments, packages over 1 lb, and flat-rate shipping for heavy items.
Delivery Time: 1-3 business days.
Flat Rate Options: If it fits, it ships for one low price, regardless of weight (up to 70 lbs).

3. Priority Mail Express®

The fastest domestic service available from USPS, offering a money-back guarantee.

Best For: Urgent documents and overnight delivery needs.
Delivery Time: Next-Day to 2-Day guarantee.
Cost: Significantly higher than standard Priority Mail.

What Are USPS Zones?

USPS uses a "Zone" system to calculate shipping rates based on distance. Zones range from 1 (local) to 9 (Freely Associated States).

Zone 1: 1-50 miles radius.
Zone 2: 51-150 miles.
Zone 3: 151-300 miles.
Zone 4: 301-600 miles.
Zone 5: 601-1000 miles.
Zone 6: 1001-1400 miles.
Zone 7: 1401-1800 miles.
Zone 8: 1801+ miles.
Zone 9: US Territories (Guam, Puerto Rico, etc.).

You can find your specific zone by using the Official USPS Zone Chart. Simply enter your origin zip code to see the zones for every other zip code in the country.

Retail Rates vs. Commercial Rates

The rates shown in this calculator are Retail Rates—the price you pay at the Post Office counter. However, you can save significantly by accessing Commercial Rates.

Commercial rates are discounted postage prices typically reserved for high-volume shippers, but anyone can access them using online shipping software like Pirate Ship, Stamps.com, or Shippo. These services can offer discounts of up to:

40% off Priority Mail rates.
25% off Ground Advantage rates.

If you ship frequently, never buy postage at the retail counter. Print your labels at home to save time and money.

Tips to Reduce Shipping Costs

Shipping can eat into your profits or budget quickly. Here are actionable tips to keep costs low:

Use Flat Rate Boxes for Heavy Items: If you are shipping dense items like books, metal parts, or liquids, Flat Rate boxes are a lifesaver. A 50lb box ships for the same price as a 2lb box if it fits in the Flat Rate packaging.
Weigh Accurately: A package that weighs 1 lb 0.1 oz is charged at the 2 lb rate. If you can remove a small amount of packaging to get it under the pound mark, you can save significantly.
Use Poly Mailers: For non-fragile items like clothing, use lightweight poly mailers instead of cardboard boxes. This reduces both the package weight and dimensions.
Check Dimensional Weight: For large, lightweight boxes, USPS charges based on "Dimensional Weight" (DIM weight). If your box is large but light, you might pay for a 20lb rate even if it only weighs 5lbs. Use the smallest box possible.

USPS Rate Calculator