Flat Rate Shipping Labels: Complete Guide for All Carriers

Flat rate shipping means one fixed price regardless of package weight, as long as the shipment fits in the carrier's designated box or envelope and stays within the weight ceiling. All three major US carriers — USPS, FedEx, and UPS — offer flat rate programs, each with different box sizes, price points, and eligibility rules.

Whether flat rate saves you money depends on what you're shipping. A dense, heavy item stuffed into a small flat rate box almost always beats dimensional weight pricing. A light item in a large flat rate box may cost more than standard shipping. This guide covers every flat rate option, current pricing, and a simple framework for deciding when flat rate is the smarter choice.

USPS Priority Mail Flat Rate

USPS Priority Mail Flat Rate is the original flat rate program and still the most widely used. Any item that fits in the official USPS flat rate envelope or box ships at a fixed price with 1–3 business day delivery anywhere in the contiguous US. You get free tracking and up to $100 of insurance included.

USPS provides the flat rate boxes free of charge at post offices and through usps.com. You must use the official USPS-branded flat rate packaging — you cannot substitute your own box or envelope.

• Flat Rate Envelope (12.5×9.5 in): ~$10.40 retail / ~$8.05 commercial — max 4 lbs
• Legal Flat Rate Envelope (15×9.5 in): ~$10.75 retail / ~$8.25 commercial
• Padded Flat Rate Envelope (12.5×9.5 in): ~$11.00 retail / ~$8.55 commercial
• Small Flat Rate Box (8.625×5.375×1.625 in): ~$10.40 retail / ~$8.05 commercial
• Medium Flat Rate Box — Top Loading (11×8.5×5.5 in): ~$16.50 retail / ~$13.35 commercial
• Medium Flat Rate Box — Side Loading (14×12×3.5 in): ~$16.50 retail / ~$13.35 commercial
• Large Flat Rate Box (12×12×5.5 in): ~$22.25 retail / ~$18.90 commercial
• APO/FPO/DPO Large Flat Rate Box: ~$22.25 retail

FedEx One Rate

FedEx One Rate is FedEx's flat rate program available for Express services (FedEx 2Day, Express Saver, and Overnight). Like USPS, you must use official FedEx One Rate packaging. Unlike USPS, FedEx One Rate is zone-independent only for 1–2 lb packages; heavier shipments have a weight-based surcharge on top of the flat rate.

FedEx One Rate packaging is available free at FedEx locations and through fedex.com. The program is best suited for small, time-sensitive parcels where the predictability of flat-rate pricing matters more than absolute cost minimization.

• FedEx One Rate Small Box (10.875×1.5×12.375 in): ~$12–$13 for 2Day service
• FedEx One Rate Medium Box (11.5×2.375×13.25 in): ~$17–$19 for 2Day
• FedEx One Rate Large Box (12.375×3×17.5 in): ~$22–$25 for 2Day
• FedEx One Rate Extra Large Box (11.875×10.75×11 in): ~$29–$33 for 2Day
• FedEx One Rate Envelopes and Paks: start at ~$9–$10 for 2Day

UPS Simple Rate

UPS Simple Rate is UPS's flat rate offering, available for UPS Ground and select Air services. Unlike USPS and FedEx, UPS Simple Rate does not require carrier-provided packaging — you can use any box that fits within the size tier dimensions. This flexibility makes it convenient if you already have your own branded packaging.

UPS Simple Rate is priced by box size tier (XS through XL) regardless of destination zone, and applies to packages up to 50 lbs. Pricing reflects Ground service; Air options add a surcharge.

• XS (fits in a shoebox, max 13×11×2 in): ~$11.95
• Small (max 16×13×3 in): ~$14.95
• Medium (max 18×14×8 in): ~$17.95
• Large (max 21×17×12 in): ~$20.95
• Extra Large (max 27×17×17 in): ~$29.95

When Flat Rate Beats Weight-Based Pricing

Flat rate wins when your package is heavy relative to its size, ships a long distance, or when the predictability of fixed pricing matters for your business model. Here's a practical decision framework:

1. Weigh your item and measure its dimensions — get the actual weight and calculate dimensional weight (L×W×H ÷ 139 for USPS, ÷ 139 for UPS Ground, ÷ 139 for FedEx Ground)
2. Note the destination zone — flat rate is most valuable for long-distance zones (Zones 7–8), where per-pound rates climb highest
3. Get a weight-based quote from your carrier's rate calculator using actual vs dimensional weight
4. Compare against the flat rate box price for the smallest box your item fits in
5. Factor in packaging cost — USPS flat rate boxes are free; UPS Simple Rate uses your own box
6. Choose flat rate if the flat rate price is lower, or if the small premium buys meaningful pricing predictability for your operation

How to Create a Flat Rate Shipping Label

Creating a flat rate label is the same process as any other shipping label — you're just selecting the flat rate service and box type when you set up the shipment.

On ShippingLabel.co, enter your addresses and package details. When selecting the service, choose USPS Priority Mail Flat Rate (or the specific box size), FedEx One Rate, or UPS Simple Rate from the carrier options. The label generator will format the label correctly for the flat rate service.

For USPS flat rate specifically: the box dimensions you enter should match the flat rate box you're using. The postage amount will reflect the flat rate price, not a weight-calculated price. Print on 4×6 thermal paper or half a letter-size sheet.

Flat Rate Restrictions and Common Mistakes

Flat rate programs have real limitations that catch shippers by surprise. Know these before you commit to a flat rate label:

• Weight ceiling: USPS flat rate boxes have a 70 lb maximum — if your item is very dense and approaches this limit, verify actual weight before printing
• Must use official packaging: USPS flat rate labels are only valid on official USPS flat rate boxes and envelopes — no substitutions
• Items must fit with the box closed: you cannot overstuff and tape the lid shut — the box must close and seal normally
• Hazmat restrictions: flat rate boxes cannot be used for hazmat materials regardless of quantity
• No zone advantage for FedEx: FedEx One Rate pricing varies by service level (2Day vs Overnight) but is zone-independent only within certain weight thresholds
• International availability: USPS flat rate Priority Mail International is available but at much higher prices than domestic flat rate

Where to Print a Flat Rate Shipping Label

Flat rate postage is meaningfully cheaper online than at the post office counter. Three primary places to print:

• USPS Click-N-Ship (usps.com): the official path. Sign in, select Priority Mail Flat Rate, choose your box size, enter addresses, pay. Includes free $100 insurance and free pickup scheduling. Commercial base rate.
• Pirate Ship (pirateship.com): commercial Plus rates — typically $0.50–$2 cheaper per label than Click-N-Ship. Free account, no monthly fee. Same Priority Mail Flat Rate service, same delivery times, same insurance.
• ShippingLabel.co: format-only label generator. Useful when you have postage from a UPS account or want to print a clean draft before committing to postage.
• Stamps.com or ShipStation: paid platforms with batch processing — worth it if you ship 50+ flat rate labels per month.

How to Schedule Free Pickup with a Flat Rate Label

Once you've printed a flat rate label and packed your box, you don't need to drive to the post office. USPS offers free home pickup for any Priority Mail or Priority Mail Express shipment, including flat rate boxes:

1. Go to usps.com → Send → Schedule a Pickup
2. Enter your address, select the date (next-day pickup is usually available), and tell USPS where to find the package (front porch, back door, mailbox)
3. Confirm and submit — your regular mail carrier collects it during their normal route, no signature or interaction required
4. Pickup is free; only Express Pickup On Demand carries a fee

Real Flat Rate vs. Weight-Based Pricing Comparisons

These illustrative examples show when flat rate wins and when weight-based wins. Prices are commercial base; actual rates vary by zone and date:

• Scenario 1: 10 lbs, NYC → LA. Priority Mail weight-based: ~$23. USPS Medium Flat Rate Box: ~$13.35. Flat rate wins by ~$10.
• Scenario 2: 1 lb, NYC → New Jersey. Ground Advantage weight-based: ~$5.50. USPS Small Flat Rate Box: ~$8.05. Weight-based wins by ~$2.55.
• Scenario 3: 25 lbs, Chicago → Texas. Priority Mail weight-based: ~$45. USPS Large Flat Rate Box: ~$18.90. Flat rate wins by ~$26.
• Scenario 4: 4 lbs in a small box, NYC → Boston. Priority Mail weight-based: ~$12. USPS Small Flat Rate: ~$8.05. Flat rate wins by ~$4.
• Scenario 5: 2 lbs of clothing in a Medium Box, Atlanta → Seattle. Ground Advantage weight-based: ~$11. Medium Flat Rate: ~$13.35. Ground Advantage wins by ~$2.35.

Insurance and Add-Ons Included with Flat Rate

Flat rate shipping bundles several add-ons that would cost extra on weight-based services:

• USPS Priority Mail Flat Rate: free $100 insurance, free tracking, free Saturday delivery, free Hold for Pickup at recipient's local post office
• USPS Priority Mail Express Flat Rate: free $100 insurance plus money-back guarantee on missed delivery commitments
• FedEx One Rate: free declared value coverage up to $100, free tracking
• UPS Simple Rate: free declared value up to $100, free tracking — no Saturday delivery on Ground tier
• Higher insurance: USPS adds insurance at $1.65 per $100 above the included $100, up to $5,000 maximum
• Signature confirmation: available as paid add-on at all three carriers, ~$3.45 USPS, ~$5–$6 FedEx, ~$5 UPS

International Flat Rate Shipping

USPS is the only major carrier with a true international flat rate program: Priority Mail International Flat Rate. Pricing is significantly higher than domestic — typically $40–$120 per box depending on destination zone — but for heavy international packages it remains the most predictable and often the cheapest option.

FedEx and UPS do not offer international flat rate services. For international shipments through FedEx or UPS, you'll always pay weight-based pricing.

• USPS Priority Mail International Flat Rate Envelope: ~$40–$60 depending on zone
• USPS Priority Mail International Small Flat Rate Box: ~$45–$65
• USPS Priority Mail International Medium Flat Rate Box: ~$80–$100
• USPS Priority Mail International Large Flat Rate Box: ~$110–$130
• Customs declaration form (CN22 or CN23) is required and auto-generated when you create the label online
• Transit time: 6–10 business days to most major destinations, longer to remote areas or during holiday season

Common Use Cases for Flat Rate Labels

Knowing when to use flat rate vs weight-based pricing comes down to recognizing the patterns in your shipments:

• eBay sellers: flat rate is great for heavy items like books, tools, and small appliances; weight-based wins for light apparel
• Etsy sellers: small handmade items often fit in the Small Flat Rate Box at $8.05 — competitive for items shipping cross-country
• B2B small parcels: the predictability of flat rate simplifies invoicing and customer-facing shipping costs
• Subscription boxes: known package size and consistent contents make flat rate ideal for predictable monthly cost
• Long-distance personal shipments (gifts to relatives across country): flat rate beats weight-based for anything over 2 lbs going Zone 7–8
• Returns to a single warehouse: businesses processing many returns from across the country benefit from flat rate's zone-independent pricing

Frequently Asked Questions

Are USPS flat rate boxes really free?

Yes. USPS provides free flat rate boxes and envelopes — you only pay for postage. Order online at store.usps.com → Free Shipping Supplies, or pick up at any post office.

How long does flat rate shipping take?

USPS Priority Mail Flat Rate: 1–3 business days. FedEx One Rate: speed matches the chosen Express service (2Day, Express Saver, Overnight). UPS Simple Rate: 1–5 business days for Ground tier depending on zone.

Can I use my own box for flat rate shipping?

Only with UPS Simple Rate — UPS doesn't require carrier-branded packaging. USPS and FedEx flat rate require their own official boxes.

What's the maximum weight for flat rate shipping?

USPS: 70 lbs in any flat rate box. FedEx One Rate: 50 lbs. UPS Simple Rate: 50 lbs across all tiers.

Is flat rate cheaper than Priority Mail standard?

Sometimes. Flat rate beats standard Priority Mail when the package is heavy or going far. Standard Priority Mail beats flat rate when the package is light or going short distances. Always compare both before printing.

Can I track flat rate shipments?

Yes. Every flat rate label includes a free tracking number active from acceptance through delivery.

Does flat rate include insurance?

USPS Priority Mail Flat Rate includes free $100 insurance. FedEx One Rate and UPS Simple Rate include declared value coverage up to $100. Higher coverage available as paid add-on.

Can I ship flat rate internationally?

USPS offers Priority Mail International Flat Rate boxes and envelopes. FedEx and UPS do not have international flat rate options — both use weight-based pricing for international.

What happens if my flat rate box is too heavy?

USPS automated scales weigh every package. If you exceed 70 lbs, the package is rejected and either returned to you, charged at the standard rate, or held until you pay the difference.

Can I drop off a flat rate box at any USPS location?

Yes. Flat rate boxes can be dropped at any post office, in a USPS collection box (if it fits), or scheduled for free home pickup. They're treated like any other Priority Mail shipment.