Make $4.75 USPS Flat Rate Shipping Box


Introduction: Make $4.75 USPS Flat Rate Shipping Box

This is my first instructable. I invite feedback, coaching, and correction.

My wife finally started selling stuff on the internet. One of the big things that distinguishes sellers is shipping costs. If what you are selling (in our case used boutique baby clothes) is heavier that 13oz. you have a lot of options* of how to ship. The same package could cost you $8.60, $10.95, or $4.75 depending how smart you pack it. I was able to package 2 shipments by hand in about 40 minutes. Once I made the jig I could do it in 3 minutes flat.

* Technically you have one les option, since the cut-off for the cheaper first class mail is 13oz.  If you can ship first class, you should. It's the best value. So, for packages 13ox and under, I think there is really only 1 choice.

Step 1: The Supplies

Here is what you need.

1. A 12 1/2in x 9 1/2in Flat Rate shipping envelope, price $0.00
2. A strip of plywood* ripped down to a width equal to the shortest dimension of your box, price $2.00 or free (scrap)
3. 8 wood screws 1 1/4in length or longer, price $1.79 or free (scrap)

Table Saw for ripping the plywood (not needed if using a 2x4)
Miter Saw for cutting the sides to length
Philips P2 bit (or T20 if using DeckMate, the only wood screws I use)
Counter sink bit (recess the screw heads, it's prettier)
Forstner bit , Wood Spade , or Auger

* You can opt for a simple 2x4 if you don't have a means of ripping the plywood, but it won't be very useful for stuffing.

Step 2: Measure Twice

Here is the paradox:
The measurements don't really matter, but they must be precise.

The width of the strip of wood should be placed against an edge of the envelope and the remainder of the envelop measured. Repeat on the perpendicular edge. Make sure to fold the flap upward so that you don't add it to the measure.

The measurements I ended up with were:
3 3/8
9 1/8
6 1/8

The thickness of the plywood was 11/16. I accidentally rounded down to 5/8. If you are going to round, round up. For your benefit, I will use 3/4 in the measurements below.
IF your wood is ripped to 3 3/8in and is 3/4in thick , Cut the pieces to:
2x  8 3/8 (that's 9 1/8 - 3/4)
2x  5 3/8 (that's 6 1/8 - 3/4)

This also assumes what I call "pin wheel" construction which I prefer because you are only screws into one end of each board. This lessens the chances of splitting. If I did the "sides inside" construction I would cut one pair to the length measured, and the other pair would be shortened 1 1/2in.

Step 3: Assemble

Mark and drill all of the holes before you start assembling. When you bore the hole, make sure you have a board underneath it that you can drill into so that you avoid the "tear out" that occurs from free air drilling.

I didn't bore both sides of mine. This causes a vacuum when trying to remove the jig. I will go back and bore the other side.

Don't forget what you are doing when you start putting the box together. Notice the "pin wheel" construction. Once you cut it this way, you have to follow through.

Step 4: Use the Jig, Luke

1. Use shipping tape to reinforce the corners before you start. (This is much easier to do to a flat envelope.)
2. Insert the sideways and carefully form the first corner crease.
3. Rotate the whole thing and crease the 2nd corner.
4. Remove, rotate 90°, and reinsert the jig, being careful not to rip the corners.
5. Fold in the flaps.
6. Flip the whole thing over so that the table is holding the flap closed.
7. Carefully crease the final corners.
8. Use the bore hole to retrieve the jig.

Step 5: Fill and Ship

You can use the jig to estimate and shape your payload. When shipping clothing, I prefer to stuff everything into a Tyvek or zipper seal bag. It keeps the contents safer (especially the Tyvek) and dry. I then stuff the bag into the jig and apply the shipping tape in such a way that the shape is maintained by the pressure from the tape and not the vacuum of the squeezed out air.

Put your bound payload into the box and seal with the provided strip making sure to avoid wrinkles. Reinforce your seal with shipping tape. I strongly suggest using clear shipping tape (yes there is also brown shipping tape) so that your package still looks like a Flat Rate shipping envelope. Remember, if they think you have altered the envelope, they may refuse to accept it for the special flat rate. Your package can be up to 70 lbs. If it were to contain a 3 3/8 x 9 1/8 x 6 1/8 block of lead, that would be 77lbs 4oz.

If you use masking tape or office (scotch, magic, crystal, etc.) tape they will reject your package outright. Don't taunt them on this.

If you order online and print your own shipping the cost is $4.75, if you go into the post office it is $4.95.

Enjoy saving 50% or more on you shipping!



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    33 Discussions

    So what we have now is sellers stuffing Flat Rate Boxes inside the Flat Rate envelope to save a lousy 25 cents, how smart is that.

    4 replies

    There is always that one guy that feels the need to comment with a negative comment just to put other people down.

    Don't pay attention to these people. Personally, I would so use this for my shipping. And even if it is saving 25 cents it's still worth it when you mail 1000 packages a month.

    Thank you so much for sharing.

    Current USPS Retail Prices:

    $5.75 Priority Mail™ Small Flat Rate Envelope

    $5.95 Priority Mail™ Small Flat Rate Box

    Sorry you are right it's not 25 cents, it's 20 cents, 20 lousy cents!

    you can fit at least twice the volume in the envelope

    Maximum thickness 1/4 inch ... Letters, large or thick envelopes

    Your idea won't work and steers people the wrong way as it would lead to damage, postage due, return to sender, etc etc....

    Besides, peoples time is worth something -- don't you think?

    1 reply

    Bro if they state 1/4" max (do they?) I can assure you they do NOT enforce it, flat rate is flat rate with these. As long as it's not prohibited materials, you can mail a brick of lead, even wrap the damn thing in tape, they don't care.

    Hello Non flatrate shoebox by USPS. How much might you cost if you're just three pounds? Huh? Seems I have to go wait in line to get this thing priced no matter the paypal postage service or the Ebay paypal service.

    Most post office have automated mailing stations in front by the mail boxes.

    As long as you didn't modify the box AND it shuts properly without additional tape it SHOULD work however many Post Office workers are on the lookout for these things and they may not accept it. Also the cutoff on 1st class mail is 16 oz, not 13 so it still may be cheaper to use 1st class mail depending on your item. My best tip is to use a site like which offers discounted postage rates which are cheaper than the Post Office directly.

    1 reply

    First class mail weighing over 13 oz. not bearing a metered label, MUST be taken to the post office!

    Priority Mail padded flat rate envelopes are also free and a cost effective shipping packaging. The current USPS rates also make the Priority Mail legal flat rate envelope the same price as the standard envelope.

    I showed this to my husband, and he made it for me. I just can't seem to follow the instructions for making the folds, esp. the first one. When I tried it, the box ended up longer than the jig, not a tight fit at all. Could you add a video or more pictures with details of using the jig in the envelope?

    This sounds useful if you need a box a little larger/deeper than the small flat rate box ($5.95) but do not want to bump up to the Medium flat rate box ($11.30).

    It looks like the small flat rate envelope price increased since you posted this four years ago.


    3 years ago

    Ok the priority flat rate boxes do have to stay in the shape as it is with no buldging showing. Flat rate envolopes can be stuffed but as long as it closes with no tape then ya should be good... If it is taped shut and the end of envolope is t shut all the way there is a chance ya will het it returned.

    This is prohibited per the Postal Domestic Mail Manual (Eg, postal regulations) If you use flat rate priority packaging, you are not allowed to modify the package shape. It must remain the same shape and size as when you got it - doing this is a great way to have your package get damaged on the sorting machines at the post office and/or have it RETURNED for standard postage (or delivered postage-due)

    If you want to make custom-shaped boxes, you can use the NON flat rate packaging materials, and then pay proper postage based on weight/etc.

    USPS shipping is far cheaper than UPS or Fedex, why do you feel the need to cheat them out of a couple bucks?

    1 reply

    The prohibition is that you are not allowed to change the packaging by cutting it, and you must be able to close the package with the seal that is there--simply folding the corners is legal.

    I use a similar method, often. The envelope will hold more than twice as much as the small box, for the same price. Since it is priority - if the items you're shipping are heavy and/or small - the priority tape is at your disposal; use it liberally. This will keep prying eyes and hands out of the envelope and avoid it "accidentally" breaking open. I mummify my shipping packages at USPS, since I've had bad experiences with them "losing" much of the contents in a USPS facility. Use the electronic kiosk to avoid hassle from nosy USPS employees and speed the process of shipping. I use my phone to shoot a picture of the label before shipping for easy tracking and to send to the recipient.