Adult Onesie From a T-Shirt




For those of you that don't know a onesie is a t-shirt with snaps in the crotch.  You can pick the up everywhere for babies but for an adult you need to order form a specialty dealer.  They normally start at $25 plus shipping and go up from there.


Step 1: Materials

For this project you will need.

1. A T-Shirt a few sizes too big.  I wear a size large and used a 2XL
2. A t-shirt that fits for a pattern
3. Scisors
4. Sewing equipment.  I sewed mine by hand but a machine would be faster.
5. Pins. Lots of them.
6. A marker or chalk for lay out.
7. A tape measure
8. Snaps.  I used sew on snaps but Velcro could also be used. (9mm shown in picture have since been replaced with stronger 21mm)

Step 2: Layout

1. Turn the large t-shirt inside out and spread out flat.

2. Lay the smaller t-shirt on to of it with the tops aligned

3. With the marker or chalk draw a line straight down from the armpit seam of the large t-shirt to the bottom along the smaller shirt on both sides.

4. Take your round object and trace a radius from the line you just drew to the armpit of the t-shirt.

Step 3: Pinning

1. While keeping everything flat put many pins along the lines on both sides all the way to the bottom.

2. Carfuly slip the shirt on and decide where the split for the legs will be and mark it.

Step 4: Sewing the Sides

Sew from the armpit all the way down to the mark you made for the split.  It is a good idea to re-enforce the bottom of the split with some extra stitching.  I use a double row of hand stitching.

Step 5: Cutting

Leaving a centimetre or so of extra cut along the outside of you seems.

Step 6: Laying Out the Crotch

1. Fold the shirt in half.

2. Decide how wide you want the crotch and divide than number in half.

3. Make a mark half the desired width from the centre.

4. Lift up each layer and transfer the mark to it.  There should be four marls all the same distance from the centre.

Step 7: Pinning the Crotch

Step 8: More Sewing

Sew along your line of pins to form a hem.

Step 9: Triming

Cut off the triangles of material to complete the hem.

Step 10: Putting on Snaps

1. Turn the t-shirt back right side out.

2. Turn the bottom edge of both sides up.  Arrange them so they are close together.  THis way you will be able to see where to place the snaps on both sides.

3. Sew the first snap on both from and back.

4. snap the together and leave them that way while you do the others so they will all line up.

Step 11: Finished

To improve the fit next time around I will be starting with a larger shirt so I can position the snaps more to the front rather than in the middle.  I would also not make the front and back identical but rather the front slightly narrower.



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    16 Discussions


    Question 10 months ago

    So for the split it that where the snaps will go?


    1 year ago

    This was soooooo helpfull thanks so much!


    3 years ago

    if my shirt size is XL what size shirt do i need to buy so then i can make one of these? please let me know by this email thanks ^.^


    3 years ago

    I am definitely going to make this when i got a little more time probably before halloween though


    3 years ago

    I tried this but instead of an oversized mens shirt i bought a women's long tshirt, the kind that's almost long enough to be a dress, and i didn't have to do any trimming or sewing anywhere but at the bottom where i didnthe cut outs for legs and put on the snaps. Worked really well.


    I have come back to this again and again over the years to make interesting onesies, including Captain America, Tigger and a light up Iron Man Arc reactor.

    This is freaking awesome, whatever you want to use it for. Only thing is, if your fairly tall, t-shirts do get wider, bu not a lot longer all the time, so you will need a VERY large shirt. Or a small adult.

    Many thanks for the idea though!

    I want to make onesie for the Rugby World Cup! imagine... crashed out in the lounge with all your rugby buddies cheering on your favourite rugby team...wearing onesies of your country! a south-african onesie of springbok and RSA flag design, a nz onsie of the all black and nz silver fern or nz flag design, and the english supporters sitting there wearing the england rose design... and Australia? well there is bound to be at least one aussie with ya! aussie flag / wallaby design for be cool! first i have to see if spotlight or anywhere else had the material coz i dont want to ruin a tee-shirt. lol


    I have a 21 year old mentally and physically handicapped son and he is constantly putting his hand down his pants and ripping his diaper. To buy these shirts costs approx $25 each. I can sew and saw this and thought why not try making my own. That's why it's handy and useful for me. I didn't care for having to purchase a membership just to download the pdf file but it was only the cost of one of the ones you buy, so if it works its a win win situation.


    8 years ago on Introduction

    This is perfect for my constant worry of everyone behind me seeing my crack when riding (motorcycle, that is). Genius!


    8 years ago on Introduction

    Great idea, though most people won't find a use for it.