A Very Simple Bento Bag Tutorial : The Math

Hello All ~~

I came across a very, very simple drawstring bento bag pattern; thinking it would be a delightful project to share as a tutorial.  However, when the bag was complete, it seemed a bit small, barely fitting my 4.5" square bento box. So I worked on a 'formula' (did I tell you I'm a numbers geek?) to  customize a pattern to fit your bento lunch box. 

The bento lunch bag is a basic drawstring bag but what I like about it is how the bottom is done; a different method from the commonly used boxed corner.


To determine HEIGHT for your pattern
1) Measure height for your bento lunch box =  h"
2) Add drawstring tunnel allowance =  +2.0"
3) Add top and bottom seam allowance = +1.0"
4) Add bottom fold allowance:
     a) Measure the shorter width at the bottom of your box
     b) Divide that measurement by 2 : add to height = +x"
5) Add allowance for extra room at top of bag = +2.25"

To determine WIDTH for your pattern
1) Measure width for your bento lunch box = w"
2) Add allowance for room needed when bag is 'closed' with the drawstring = +5.0"
3) Add allowance for side seams = +1.0"

You see...a numbers geek am I !  :-B   With this formula, making a bag to fit a square or rectangle container shape should be a help.  If you are unsure about the fit, making a test piece is a good thing.

Now for the fun part.  After calculating your measurements; here is how you put the bag together.

STEP 1 :Cut 2 pieces using your pattern measurements (there is no lining or interfacing for this style)

STEP 2 : Finish all edges with an overcast stitch or zigzag or stitch of your choice

STEP 3:  Place fabric pieces right sides together and sew along bottom edges with pressure foot (align pressure foot along edge of fabric and sew OR sew with a 1/4" seam).

STEP 4: Mark the line for the bottom fold : Use the bottom fold allowance you used in calculating the HEIGHT.  IMPORTANT : Measure from the sewing line on the bottom.  Do this on both sides. Repeat for second fabric piece.

STEP 5 :Fold along bottom fold line; with right sides together, press.  Repeat for second fabric piece.  In this step you are forming the base of the bag; similar to doing a boxed corner but with a different method.

STEP 6: Bring the two folds together; creating a valley fold in between the 2 fabric pieces; lightly press fold in place. (see above pic)

STEP 7: Mark 2" from the top for the drawstring tunnel.

STEP 8: Pin sides.  Sew along each side up to the drawstring mark.

STEP 9: To finish drawstring tunnel; fold over 1/4"; press.  Then fold edge to drawstring line to form tunnel; press.  Sew along edge.

STEP 10: Cut 2 cords; 23" in length each.  Pull a cord through each drawstring tunnel. Tie ends.

A couple of notes :

In the 'formula', One Inch is added for the seam allowance although it may be less. Hey, this is a bag so an exact measurement is not needed.  But with the extra allowance you can finish the edges by turning over the raw edges and sewing in place instead of using a cast over stitch or zigzag.

Feel free to adjust the height of the bag so that you can fit a couple of lunch containers in your bag.

Your bag may fit a couple different containers, close in size.  If you don't want to do any calculations here are a couple of sizes for you to have fun with :

To fit a 3.5" (h) x 7.25" (w) bento lunch box :
Pattern Measurement : 10.5" (h) x 13.25"(w), Bottom Fold : 1.75"

To fit either a 2.75" (h) x 5.5" (w) lunch box or 4.5" (h) x 4.5" (w) lunch box
Pattern Measurement : 10.75" (h) x 11.50"(w), Bottom Fold: 2.75"

This pattern is so simple and quick that these bags will make great Christmas gifts! You can use the bag to hold a 'ziploc' container filled with cookies or candies, a scented candle, jars filled with cookie mixes, etc.  The bag can be a lunch bag or a bag to carry electronic devices, jewelry, scrabble pieces, etc.

I added a couple of "hello kitty" bows to add a bit of cuteness

Thank you dear followers for visiting with me and crafting along; I feel privileged to have your company ^*^


  1. this is a great project. Thank you for sharing it. I will add it to my 'things to make for my family list' (admittedly a very long list!)

    kate x

  2. This is gorgeous and your fabric choice is lovely. Tutorials are always welcome, thanks for taking your time to teach us new things. Keep it up girl! <3

  3. Hi Kate ! Oh Oh..I have lists too..and at least a hundred bookmarks (^*^) ... heh. too many things to make and sooo little time ^^

  4. Hi Yadira ! Can't go wrong with Hello Kitty .. she's makes everything cute ^^ I'm glad you like the tutorials ^^ The tutorials take a whole lot of time & sometimes I wonder why do I do this? So thank you soooo much for your note ^^

  5. Kat, about the topic you asked me about. There are MANY options on eBay and Etsy but it all depends on what would you like. Ive had chance to do some research and I'd love to be useful. Let me know more or less what would you like through my e-mail and I'll answer as shortly as possible.

    irisy.riveraortiz (a) gmail.com

    I don't want to spoil any surprise. :D

  6. Hi! I just discovered Bento lunches recently and your blog today. I am relatively new to sewing, plus I taught myself only about six months ago. My daughter will be in kindergarten next year so I am giving myself plenty of time to figure out how to make the perfect bag for her lunches! This one looks perfect as I can make it to fit the container I want to use (thanks to your formula!) but can this be made with laminated fabric and/or somehow insulated? She LOVES Hello Kitty...where did you find the fabric..so cute!

  7. Hi Kelly..welcome :0)

    I'm not sure if a laminated fabric would work because of the drawstring section, it may be too stiff. I have another bento bag tutorial where you could use laminated fabric as the lining. http://zakkainspired.blogspot.com/2010/07/kawaii-bento-lunch-bag-tutorial.html

    Not sure if you read this post on bentos, i have a link to a bento blog by a mom in Hawaii .. Cute ideas ! http://zakkainspired.blogspot.com/2011/09/bento-oh-bento.html

    I bought the HK fabric in Japan but you may be able to find similar fabric on etsy. Happy hunting.

    Sewing is addictive! Since I started sewing, I have become very good at ripping out seams! No joke :0)

    Oh, if you use the simple bento bag tut, I recommend using cheapo fabric first to do a prototype to see if you like how it looks.

  8. Kat,

    Thanks so much for the quick reply. I have quickly become addicted to sewing and my "want to sew" list is getting very long!

    The problem I am having with various patterns for bags that I have found (an I do like the other bag tutorial you have) is the size. There are two possible containers I would like to use at the time and one of them won't fit in ANY bag I have seen. The other one might. I just don't have the skills to alter the patterns myself, but like I said, I have got time to figure it out.

    I have bookmarked your blog and will check back often.

    Kelly :)

  9. The bento bag looks amazing,just adorable. I am a beginning sewer and have my heart set on making this my very first sewing project!!! That fabric is just great. Could you crochet a cord instead of using proper cord? just don't quite understand step 5-9 or so. Plz clarify and maybe make a video or something. It's a bit childish of me to ask i know, but I'm only 13!!
    Thanks so much
    p.s(wear that apron loud and proud)you're the only person that ever responds to all my comments,AMAZING

  10. And also, can lining be added?, just to neaten it up and if so, how would it be done.can handled or straps be added in somehow? Where's the best place to find good quality cheap fabric to begin sewing. My budget is £10 and ikea don't sell Japanese fabric. Ideas?

  11. Hi Kat. Thank you so much for sharing this bento tutorial with us. I think it is so adorable. I am new to sewing and i understand up to number 5 and after that i dont know what to do. I was wondering if you could show more pictures of how you get the sides folded up to a point where you put the bow. I dont know about how far in to sew the edges and i dont know how you got the point for the bow. Thank you so much for your time and for sharing. Beautiful work!!!!

    1. Hi Sarah!
      not sure when I'll be able to get
      back to my blog, I found this tutorial that might be better at showing the steps. It uses a different method but the result is the same


      As for the bow, if I remember correctly, it begins with a circle shape.

      Thanks for visiting!!

  12. Thank you so much! It helped a lot!
    Keep up the beautiful work i love it all!
    Thanks again,