Introduction

Last month I spent 18 minutes trying to find a box for returning a pair of boots to a small online boutique. I eventually cut up an old Amazon cardboard box (don’t ask why) and taped it so many times it looked like a kindergarten project. And because the return wasn’t prepaid, I had to figure out how much it would cost to ship something myself — which led me into the rabbit hole of flat rate shipping boxes.

In 2024 alone, I made 41 returns that weren’t prepaid (I know…), and at least half of the headache wasn’t the refund; it was figuring out the cheapest shipping method, which courier fee made sense, and how long flat rate shipping takes when you actually need the refund soon. Anytime a brand made me pay return postage, I found myself juggling box sizes, UPS packaging cost, USPS weight brackets, FedEx Office closures, and my own frustration.

So if you’ve ever asked “how much does it cost to ship something?” while standing under fluorescent lights at a USPS counter, this guide is for you. And yes — we’ll talk about exactly how much to ship a large flat rate box, which is where most people overspend without realizing it.

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What Are Flat Rate Shipping Boxes (And Why They Matter for Returns)?

Quick overview: flat rate shipping boxes
Flat rate boxes let you ship returns for a fixed price based solely on the box size — not weight or distance. They’re usually the cheapest shipping method for medium or heavy returns and often reduce prep time by 15–20 minutes since you don’t need to weigh or measure anything.

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Flat rate shipping boxes are pre-priced boxes provided by carriers like USPS (Priority Mail Flat Rate), UPS (Simple Rate), and FedEx (One Rate). You choose a box size, fill it, and pay one flat fee no matter how much the package weighs.

For returns, this is a lifesaver because:

• you don’t need a scale

• you don’t need to calculate courier fees

• weight doesn’t matter

• it’s usually cheaper for heavy items

• you get predictable timing

Here’s where it gets interesting…
Most people only know USPS Priority Mail Flat Rate, but UPS and FedEx now have flat fee shipping boxes too. And depending on what you're returning, one carrier can be dramatically cheaper than the others.

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How Much Does It Cost to Ship Something 

Let’s break it down with real 2025 pricing.

USPS Priority Mail Flat Rate (most popular)

• Small Box: ~$10.40

• Medium Box: ~$17.05

• Large Box: ~$22.80

UPS Simple Rate (UPS packaging cost varies)

• XS: ~$10.20–$12

• S: ~$14–$16

• M: ~$18–$20

• L: ~$23–$26

• XL: ~$28–$32

FedEx One Rate

• Small: ~$13

• Medium: ~$17

• Large: ~$23–$25

If you’re figuring out how much to ship a large flat rate box, USPS Large Flat Rate is typically the sweet spot at $22–$23, especially for heavy returns (boots, books, kitchen items).

UPS is often cheaper for long-distance, FedEx sometimes for business returns, and USPS usually wins for heavy personal packages.

But consumers rarely know that. When I returned a pair of 4-pound kitchen pans last summer, USPS Large Flat Rate was $17 cheaper than sending the same item weight-based.

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How to Ship a Package 

This is the neutral, step-by-step return flow that applies to almost any brand when they don’t provide prepaid labels.

Step 1 — Check the brand’s return portal

You choose:

• refund or exchange

• return reason

• whether they cover postage

Step 2 — Find a suitable box

Most brands require:

• sturdy box

• padding

• the item fully sealed

I’ve reused Amazon boxes more times than I can count.

Step 3 — Tape and pack

Use packing tape, not scotch tape (learned that the hard way — one of my returns opened in transit).

Step 4 — Create a shipping label

You have options:

• USPS

• UPS

• FedEx

• Pirate Ship

• Stamps.com

Step 5 — Pay the courier fee

This depends on:

• weight

• size

• distance

• service speed

This is usually where consumers ask:
“How much does it cost to ship something?”
(And why flat rate boxes save you from weighing.)

Step 6 — Drop off

You take it to:

• USPS

• UPS Store

• FedEx Office

Step 7 — Wait for the refund

This can take 5–14 days depending on brand and carrier.

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Common Issues Shoppers Face With Return Shipping

Now the tricky part…
Shipping returns yourself often creates more pain points than the return itself.

1. Return fees

Some brands charge $4–$12 to return items.

2. Printing labels

If you don’t have a printer, it’s a problem.

3. Long refund windows

Some retailers wait 14 days after receiving the item.

4. Limited drop-off options

Not everyone has a UPS Store or FedEx Office nearby.

5. Shipping delays

I once had a package sit at a USPS facility for six days.

6. Packaging hassle

Finding a box, taping it, padding the item.

7. Multi-step verification

Some retailers require you to include order papers inside the box (yes, I’ve forgotten and had to reopen the box).

Here’s what most shoppers don’t realize…
You don’t always need to ship your return at all.

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A Shift in Returns — Alternatives That Avoid Shipping Entirely

Over the past year, new return options popped up that avoid most of these headaches — especially ones that skip shipping entirely.

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A Modern Alternative — Local, Box-Free Returns

Closo offers a new way to return items locally without dealing with flat rate shipping boxes, tape, packaging, or measuring.

How Closo works 

• No labels

• No box

• No returning to USPS, UPS, or FedEx

• Drop-off in 30 seconds

• Instant confirmation

• Refunds typically 2–3× faster

• Vetted local sellers handle the return

• Significantly greener than shipping

It eliminates all of the guesswork around courier fees, UPS packaging cost, and how much a large flat rate box costs. You simply hand the item over, and you’re done.

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Why Many Shoppers Prefer Using Closo

Closo is appealing because it removes every friction point:

• No printer

• No packaging

• No lines

• No flat fee shipping boxes

• No delays

• No courier fee calculations

• Refunds often within 48 hours

• Fewer fees than shipping

• No risk of lost packages

My own experience

I used Closo in August to return two heavy kitchen items that would’ve cost $18–$23 in shipping. Instead, I walked into a local drop-off location and got my refund two days later. Honestly, I don’t know why brands still make us figure out return postage when options like this exist.

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Flat Rate Shipping Boxes vs. Local Drop-Off

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People Always Ask Me: “How long does flat rate shipping take?”

Usually:

• USPS: 1–3 days

• UPS Simple Rate: 1–5 days

• FedEx One Rate: 1–3 days

But during holidays I’ve had USPS Priority Flat Rate take six days (yes, really).

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One Question I Get Constantly: “Is flat rate the cheapest shipping?”

For heavy returns, yes — often by $5–$12.
For light items, weight-based is cheaper.

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A Common Thing Shoppers Wonder: “How much to ship large flat rate box?”

USPS Large Flat Rate Box: ~$22.80.
If the item is over 4 lbs, this is usually the best deal.

Not all brands support Closo yet. If the retailer you’re returning to doesn’t offer it, you’ll need to use the standard return process — though many shoppers now ask brands to add Closo because it makes returns significantly easier.

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Worth Reading

Many shoppers who struggle with return shipping also explore the Closo Customer Hub, especially the sections explaining free return options and refund timing. I also reference similar return challenges in the guide about Free Returns Near Me, and you’ll see shipping-saving tips inside the article about Return Fees too.

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Conclusion 

Figuring out which flat rate shipping boxes to use — or whether flat fee shipping is even the cheapest shipping option — can turn a simple return into a stressful chore. I’ve overspent by choosing the wrong box size, driven across town to find a UPS Store, and delayed refunds because I mailed something the slowest way without realizing it. Flat rate boxes are still one of the best tools for heavy returns, but they’re far from perfect. And some brands still don’t support easier, local return alternatives.

I use Closo whenever the brand supports it — dropping off items locally saves me time, avoids fees, and gets me refunds faster.