A USPS Medium Flat Rate Box costs one set Priority Mail price to any address in the United States, no matter how heavy it is (up to 70 pounds) or how far it travels. USPS publishes a single retail price for both Medium Flat Rate Box 1 and Box 2, and labels bought online are priced at lower Commercial rates than the Post Office counter.
Because the exact figure changes with each USPS price adjustment, the fastest way to see what a Medium Flat Rate Box costs today is to compare live Medium Flat Rate and weight-based Priority Mail prices in the ParcelPath rate calculator. This guide explains what the price includes, the two box sizes, when the flat price beats paying by weight, and how 2026 price changes affect it.
How Much Does It Cost to Ship a Medium Flat Rate Box?
The cost to ship a Medium Flat Rate Box is fixed: USPS charges the same Priority Mail Flat Rate price whether the box holds two pounds or 70 pounds, and whether it goes across town or from Maine to Hawaii. The only things that change what you pay are where you buy the label and which USPS price period you ship in.
You’ll see two price levels for the same box:
- Retail price: what you pay at a Post Office counter or kiosk.
- Commercial price: the lower price USPS offers for postage bought online, through USPS Click-N-Ship or an authorized shipping platform.
Every Medium Flat Rate shipment includes USPS Tracking and up to $100 of insurance on most shipments, and the box itself is free. USPS gives Flat Rate boxes away because they can only be used for Priority Mail Flat Rate postage. If you want the full side-by-side of Small, Medium and Large box options, our guide to USPS Flat Rate box sizes and shipping costs compares every size.
What Are the Medium Flat Rate Box Dimensions?
USPS makes two Medium Flat Rate Boxes, and both ship at the same price. Box 1 opens from the top and suits bulky, cube-shaped items. Box 2 loads from the side and is flatter, which works better for books, binders and clothing.
| Box | Loading | Outside dimensions | Inside dimensions | Domestic weight limit |
|---|---|---|---|---|
| Medium Flat Rate Box 1 | Top-loading | 11-1/4″ x 8-3/4″ x 6″ | 11″ x 8-1/2″ x 5-1/2″ | 70 lbs |
| Medium Flat Rate Box 2 | Side-loading | 14-1/8″ x 12″ x 3-1/2″ | 13-5/8″ x 11-7/8″ x 3-3/8″ | 70 lbs |
Measure your item against the inside dimensions, not the outside, and leave room for padding. The box flaps must close normally: USPS doesn’t accept Flat Rate boxes that are bulging, taped into a new shape or cut down.
Does the Price Change With Weight, Distance or Destination?
For domestic shipments, no. USPS states that Priority Mail Flat Rate products ship packages up to 70 pounds to any state at the same price, which covers Alaska, Hawaii and U.S. territories. That’s the main reason shippers choose the box: you know the postage before you pack.
International shipments work differently. A Medium Flat Rate Box can travel abroad as Priority Mail International, but it’s then charged at Priority Mail International Flat Rate prices, which vary by country group, and the weight limit drops to 20 pounds. You’ll also need a customs form, and some countries restrict what you can send.
When Is a Medium Flat Rate Box the Cheapest Option?
A Medium Flat Rate Box saves money when the contents are heavy and the trip is long. Weight-based Priority Mail charges more as weight and zone go up, while the flat price doesn’t move, so dense items going to distant zones are where flat rate wins.
It’s usually the wrong choice for light packages or short trips. A two-pound item going to a nearby zone almost always ships for less by weight with Priority Mail or USPS Ground Advantage, and small, heavy items may be cheaper still with Priority Mail Cubic pricing.
| Option | How USPS prices it | Delivery | Best for |
|---|---|---|---|
| Medium Flat Rate Box | One price, any weight to 70 lbs, any U.S. address | Priority Mail, 2–3 days | Heavy, dense items going far |
| Priority Mail (weight-based) | Weight and zone | Priority Mail, 2–3 days | Light packages and nearby zones |
| Priority Mail Cubic | Package volume and zone | Priority Mail, 2–3 days | Small, heavy packages in your own box |
| USPS Ground Advantage | Weight, size and zone | 2–5 days | Non-urgent packages where speed matters less |
The simplest test is to run the package both ways before you buy. Enter the weight and dimensions in the USPS Shipping Rates Calculator and compare the Medium Flat Rate result against weight-based Priority Mail and Ground Advantage for the same ZIP codes.
How Did USPS Prices Change in 2026?
Medium Flat Rate Box prices are set by USPS and change with its price adjustments, so a price you saw last spring may not be the price today. USPS took several pricing actions on its shipping products in 2026:
- January 18, 2026: USPS’s annual shipping price change took effect for Priority Mail and its other competitive products.
- March 25, 2026: USPS announced a time-limited 8 percent increase to base postage for Priority Mail Express, Priority Mail, USPS Ground Advantage and Parcel Select, set to run from April 26, 2026 to January 17, 2027, pending review by the Postal Regulatory Commission.
- August 25, 2026: USPS announced temporary holiday-season prices for the same four products, running from October 4, 2026 to January 17, 2027, also pending Commission review.
Each of these can change what you pay for a Medium Flat Rate Box, which is why a live quote is more reliable than any price chart. Our USPS shipping rates guide tracks how each service is priced.
How Do You Ship a Medium Flat Rate Box?
Shipping a Medium Flat Rate Box takes five steps, and you never need to weigh it unless it’s close to 70 pounds.
- Get a free box. Pick one up at any Post Office or order packs of 10 or 25 from the USPS Postal Store, which delivers them free.
- Pack it. Use the inside dimensions, cushion fragile items and make sure the flaps close without bulging.
- Buy the label. Choose Priority Mail Flat Rate and the Medium box. Buying online gets you Commercial pricing instead of the counter price.
- Attach the label. Place it on the largest flat surface and cover any old barcodes.
- Hand it off. Drop it at a Post Office or collection point, or schedule a free USPS Package Pickup from your home or office.
After drop-off, the first scan confirms USPS has the box. As it nears the destination, watch for the arrival scan at the destination facility, which usually means delivery is a day or less away.
Don’t fill a Medium Flat Rate Box with hazardous materials or anything USPS restricts. Lithium batteries, aerosols and flammable liquids carry special rules, and the box’s flat price doesn’t change those requirements.
How Can You Pay Less for a Medium Flat Rate Box?
The biggest saving comes from where you buy the label. ParcelPath gives you discounted USPS pricing of up to 89% off retail on USPS services, plus up to 85% off UPS, and it’s 100% free: no subscription, no per-label fee, no minimums and no contracts. More than 44,000 customers use it to compare USPS and UPS side by side.
If you don’t have a printer, you can show a USPS Label Broker code at the Post Office counter and the clerk prints the label for you. Our page on USPS discounts explains how commercial pricing works, and the ParcelPath shipping calculator page walks through comparing services before you buy.
Two other habits help. Check whether a weight-based label is cheaper for light or short-distance shipments, and if you need it there faster, compare Priority Mail Express costs before upgrading. For shipments too big for any flat rate box, such as a full pallet, ParcelPath’s PalletPath service quotes LTL freight; our overview of flat rate freight shipping options covers when freight makes sense.
For more packaging guides, measuring tips and carrier comparisons, browse the ParcelPath shipping resources library.
Frequently Asked Questions
Is a Medium Flat Rate Box the same price to every state?
Yes. USPS charges one Priority Mail Flat Rate price for a Medium Flat Rate Box going to any U.S. state, including Alaska and Hawaii, as long as it weighs 70 pounds or less. The only price difference is between the retail counter price and the lower Commercial price for labels bought online.
Are Medium Flat Rate Box 1 and Box 2 the same price?
Yes. USPS prices both Medium Flat Rate Boxes the same. Box 1 is top-loading with inside dimensions of 11″ x 8-1/2″ x 5-1/2″, and Box 2 is side-loading with inside dimensions of 13-5/8″ x 11-7/8″ x 3-3/8″. Choose the shape that fits your item best.
How much weight can a Medium Flat Rate Box hold?
A Medium Flat Rate Box can hold up to 70 pounds for domestic shipping at the same flat price. If you send it internationally as Priority Mail International, the weight limit drops to 20 pounds and USPS charges Priority Mail International Flat Rate prices, which depend on the destination country.
How long does a Medium Flat Rate Box take to arrive?
Medium Flat Rate Boxes travel as Priority Mail, which USPS says delivers in 2–3 days. That’s an expected delivery date, not a guarantee, and it doesn’t come with a money-back refund. If you need a guaranteed date, Priority Mail Express offers a money-back guarantee instead.
Sources
- USPS: Priority Mail and Priority Mail Flat Rate
- USPS Postal Store: Priority Mail Flat Rate Medium Box (Box 1)
- USPS Postal Store: Priority Mail Flat Rate Side-Loading Medium Box (Box 2)
- USPS: Priority Mail Express
- USPS Newsroom: Transportation-related, time-limited price change (March 25, 2026)
- USPS Newsroom: Temporary price change for the 2026 holiday shipping season (August 25, 2026)
Part of our USPS Shipping Rates guide. Related: USPS Discounts, USPS Shipping Rates Calculator, USPS Shipping Calculator.
