Introduction: Bigger-on-the-Inside Tardis Bag

About: I am a scientist, professional science writer, and science educator. I'm also author of the Biology Bytes books:


One of the amazing things about the Tardis from the Doctor Who TV series is that it’s “bigger on the inside.” Of course this is impossible to do in real life, but in this Instructables project I’ve attempted to do it anyway. How? By making a small Tardis bag that’s able to open (via zipper) and be flipped inside-out to reveal a much larger bag (a canvas grocery bag). This is great if you want to keep a reusable grocery bag in the car but would like it to be fashionable and not sprawling all over.

Many other things can also be fit inside the Tardis bag – in addition to the canvas bag, I managed to include in a pair of sunglasses, a sunblock/lotion bottle, lip gloss, scissors, tissues, a pen, and a stack of quarters (in its own container). And there was still more room for other things. Check out the video in this step to see how it all fit. See the last step for a list of convenient items you could store in a bag like this in your car.

So if you want to make a bigger-on-the-inside Tardis bag that can hold all sorts of useful things you might need in your car and be able to turn into a large canvas grocery bag for those spur of the moment shopping trips, then this Instructables project is for you!

Step 1: What You’ll Need

Here’s what you’ll need to make your own Tardis bag:

  • Tardis-blue fabric. You’ll want a rectangle that’s at least 54 cm (0.6 yards) x 24 cm (0.3 yards).
  • Push pins (for holding fabric in place)
  • Tardis-blue zipper, 7” long. I used this zipper from Amazon (the 7” version) and then went to my local fabric store to find a matching blue-colored fabric. The zipper can be opened or closed on either end (ultimately it’ll be closed on both).
  • Scissors
  • Sewing machine or needle and thread
  • Ruler
  • Fabric glue. I've found that Elmer's Craft Bond Tacky Glue works great with fabric (available at Jo-Anns).
  • For use with the fabric glue, I recommend having some mini binder clips and heavy books on hand (for pressing things down while they are glued).
  • Transparent shipping tape
  • Black felt
  • White felt
  • Blue ribbon that’s about 0.5 cm wide (optional)
  • A way to attach the canvas grocery bag to the Tardis bag, if you want. I used a second zipper for this (that could open completely on one end) and used it to scrunch up the Tardis bag too.
  • A canvas grocery bag to put inside of the Tardis bag. I used a pretty big grocery bag and it worked well and there was still room to add several more things.
  • Any other things you’d like to store in a bag in your car. See the last step for a list of possibilities.

Step 2: Cutting Out the Tardis

Overall shape/dimensions

First you’ll want to cut the Tardis bag out of a piece of blue fabric. The first image in this step shows the dimensions/shape you’ll want to cut out (assuming you’re using a 7” zipper – if you’re using a different size, you’ll need to adjust the dimensions). Overall, you’ll want to cut out a 53.7 cm x 23.7 cm rectangle that has smaller rectangles (13 cm x 14.7 cm x 13 cm) coming off of the middle of the longer sides. (These dimensions include 0.85 cm for sewing seams.) The smaller rectangles will be the top and bottom of the Tardis bag. The larger rectangle will make up the main body of the Tardis bag, with a zipper joining the two short sides at the front. (If you want to see how I figured out these dimensions, see the explanation in Step 4 for making the size based on the zipper’s length.)

Fabric-cutting details and tips

To cut out the right shape, it’s easiest to use a ruler and pen to mark the lines on the blue fabric first (before cutting it) – see the pictures for examples. Then use scissors to cut out the shape on the lines. As shown in the last pictures of this step, cut 0.85 cm inward where the small rectangles attach to the larger ones, and then turn and cut 0.85 cm inward towards the small rectangle itself – this will provide some fabric for sewing the seams here.

Step 3: Sewing Up the Tardis

Sewing on the zipper

Take the 7” blue zipper, flip it upside down (so the pull tag is underneath it), and place it on top of one of the shorter sides of the larger rectangle – see the pictures for details. Position it so that the metal part of the zipper is about 3 cm from one long side (this will be the top, where the “Police Public Call Box” sign goes) and about 2 cm from the other long side. You may want to think about whether you want the pull tag at the top or bottom of the front of the Tardis (I put mine at the top). Use push pins to hold the zipper in place and then sew the edges together (one edge of the zipper with the short edge of the large rectangle) – see the pictures. Be sure to remove the push pins before sewing the area! Once done, you can flip the zipper over to make sure you like the seam.

Then attach the other short end of the larger rectangle to the other side of the zipper (sewing the underside edges together). Make sure the zipper and fabric are lined up well before sewing them together (you can again use push pins). See the pictures for how it should look when you’re done. Again, flip to the front when you’re done to make sure you like how the front of the seams look.

Lastly, I recommend using some fabric glue to glue the top and bottom of the zipper shut (see the pictures). Alternatively, you could sew them together. Somehow, it’s best to get rid of the gaps. If you use fabric glue, it’s best to use some binder clips to hold things in place while letting them glue for a couple hours. (If you make any mistakes with the glue, dab it with a little water to remove it – the glue should be water-soluble.)

Sewing on the top and bottom

Next, first make sure the inside of the Tardis is flipped out (facing you) and that the zipper is unzipped. Then fold one of the smaller rectangles over so that its unattached edge is lined up with the middle of the larger rectangle’s nearby longer edge (the middle of the longer edge should be where the zipper is) – see the pictures for details. Use push pins to hold the edges together and then sew the edges together (making sure to remove the pins before sewing that area). You can flip the bag inside out to see how the seam looks – it may be tricky to get the top of the zipper included.

Now (with the bag flipped inside-out) sew together the other two edges of the smaller rectangle with the nearby other parts of the (larger rectangle’s) longer edge. Doing this should close off this end of the Tardis. Again, you can use push pins to hold the seams together before sewing them.

Repeat this process with the other end of the Tardis so that you’ve sewed up both ends (the top and bottom of the Tardis). Once you’re done, flip it so the outside is facing you and enjoy the completely-enclosed blue bag!

Step 4: Adding Door Panels, Signs, and Windows

Figuring out the sizes/measurements

To figure out how to size and space everything on the front of the Tardis, I first found a drawing of the Tardis online (click here for the exact one I used), downloaded it, and then used a photo editing program to make it print out at the right scale as my Tardis. This means that the door opening should be the same height as the length of the metal part of my blue zipper. The first picture of this step shows the print-out with dimension/spacing measurements for each different part – I think doing this is very useful for figuring out how big to make everything and how to space it apart from each other. The second picture shows the print out with the zipper on top, showing that the door opening is the same height as the zipper’s length.

Adding door panels

You’ll want to cut six door panels out of black felt. Each panel should be a 3 cm by 3 cm square. To do this, I drew six 3 cm by 3 cm squares on a piece of paper, used push pins to attach the paper to the black felt, and then cut them out.

Next, cut out part of the inside of each square to make the squares look like the edges of the door panels. To have a shadowing effect, I made two adjacent edges of the squares be 0.8 cm thick, and the other two adjacent edges by 0.4 cm thick. See the pictures for details. The easiest way to cut this part out is to draw it on paper (on one of the cut-out paper squares you now have), put it on top of a black felt square, fold both together diagonally (using push pins), and then cut along the inside lines.

Repeat this with five of the six black felt squares so that you have five door panel edges. Leave the fifth square intact – it’s where the panel signs will be going.

Adding signs

To make the signs, I copied and pasted the signs from the Tardis image I found into a new document and printed that (to the right scale). For the “Police Public Call Box” to be the right scale, it should be about 11 cm long and 1.2 cm tall, and for the door panel sign to be the right scale, it should be about 2.3 cm by 2.3 cm. Then, to make the signs durable, put a layer of shipping tape over each sign. Carefully cut the signs out with scissors.

Adding windows

See the pictures for how I planned out the dimensions/sizes of the parts in the windows (the plans were based on a Tardis drawing). The window overall should be 3 cm long by 4 cm tall. A horizontal blue band should go across it through the middle (centered 2 cm from the top/bottom), and two vertical blue bands each centered 0.9 cm from the left/right sides. See the pictures for details. The bands should be 0.5 cm wide – you can use blue ribbon or more of the blue fabric you used for the Tardis body (the latter is what I did). To cut out the window bands from the blue fabric, I pinned my plans (to scale) to the fabric and cut out along the lines – see the pictures. Leave some extra ends on the bands so that you can wrap them around the back of the window.

To make the white part of the windows, I cut out two rectangles from white felt that were each 3 cm by 4 cm. (I marked the felt with a ruler/pen to make it easiest to cut them out.)

Once the white parts and blue bands for the windows are all cut out, glue the blue bands onto the white parts using the fabric glue. Wrap the extra blue band lengths around the backs of the white parts and glue them there too. See the pictures. (When using the fabric glue, you’ll want to put a heavy, flat object onto the gluing pieces and let them glue for a couple hours.)

Gluing it all on to the Tardis

Use the fabric glue to glue the “Police Public Call Box” on to the front of the Tardis, centered at the top right between the seam and the start of the metal part of the zipper. Use fabric glue to glue the door panel sign onto the intact door panel you made.

Then glue the windows and door panels on the front of the Tardis. Each window/door panel should be lined up right along the edge of the zipper and be evenly spaced apart from the other windows/door panels (all being spaced about 0.9 cm apart). The windows go at the very top, followed by a door panel and the panel with a sign on it, and then the other four door panels below. Make sure all door panels are oriented the same way to give a consistent shadowing effect.

Step 5: Attaching It to the Grocery Bag

I decided to attach the Tardis to the grocery bag using a

zipper, but you could do it a number of different ways. However you do it, you’ll want to flip the Tardis inside-out first – you can then attach and inside part of the Tardis to a part of the grocery bag (probably the inside of the bag is best so you won’t see the inverted Tardis then when using the grocery bag).

Scrunching up the Tardis bag with the attachment zipper

Figure out how you want the Tardis bag to look when it’s turned into the grocery bag. I decided to try and make the Tardis bag scrunch up into a small, more convenient size. To do this, I tucked in its sides and rolled it up so the two ends of the zipper came together in one spot. Then, I un-zipped the (new) zipper I used for attaching the Tardis bag to the grocery bag, and sewed one end of the open zipper to one end of the Tardis bag, and the other end of the open zipper to the other end of the Tardis bag – this means that when the (new) zipper is closed/zipped up, it scrunches the Tardis bag together! See the pictures.

Attaching the zipper to the grocery bag

Figure out where you want the Tardis attached to the grocery bag. When you’ve decided, sew the other end of the zipper to that part of the grocery bag. I attached it at the top of the grocery bag, on the inside, so the Tardis bag (scrunched up) dangles on the inside of the grocery bag.

Step 6: Filling It Up & Trying It Out

To put the grocery bag inside of the Tardis bag, unzip the attachment zipper, scrunch/roll up the grocery bag and, while the Tardis bag is inverted (inside-out), hold the grocery bag right next to the Tardis bag. Then flip the Tardis bag outside-in while keeping the grocery bag next to it, trapping the grocery bag inside as the Tardis bag gets flipped. See the pictures. (Alternatively, you could probably flip the Tardis bag outside-in and then try to shove the grocery bag inside of it.)

Depending on how big your grocery bag is, there should be plenty of room for other things that would be useful to keep in your car -- I managed to fit a spare pair of sunglasses, tissues, a stack of quarters, a pen, lip balm, sunblock/lotion, and round-tipped scissors (along with the grocery bag). (For a great way to store quarters, take an old prescription medicine container, clean it, and fill it with a stack of quarters – it works great!) Check out the video at the top to see how well all these things fit in the bigger-on-the-inside Tardis bag!

All in all, here's a list of good items that might be good to store in the Tardis bag if you're keeping it in your car (I got these ideas from here and here):

  • Spare pair of sunglasses
  • Tissues
  • Quarters
  • A pen
  • Lip balm
  • Sunblock
  • Lotion
  • Scissors
  • Hand wipes
  • A stain removal pen
  • A flashlight
  • A multipurpose tool
  • Toothbrush/toothpaste
Zip It Good! Contest

Second Prize in the
Zip It Good! Contest

Formlabs Contest

Participated in the
Formlabs Contest

Glovebox Gadget Challenge

Participated in the
Glovebox Gadget Challenge