DIY Bra Fitting Guide

Here at mysmartypants we understand that we've not been able to fit you ourselves with the bra you are considering purchasing. Experience also tells us that using a guide for calculating bra size is not always the most accurate way of determining your size. So to help you find your perfect bra size, we’ve condensed our bra-fitting techniques into a handy guide you can use from the comfort of your own home:

The Do-it-yourself Bra Fitting

1. Pick your bra style and boob type 

Before you start sizing, you need a good idea of what kind of bra and shape you’re looking for.

Do you know what shape your boobs are? Don't worry if you don't, using a simple test you can find out if you are 'Full on Top', 'Full on Bottom' or have 'Even Fullness'.

Without your bra on lean over and look where your nipples point. Do they point straight down, towards your feet or away from your body? See the picture below (courtesy of the bra fitting group Boob or Bust).


Are you Top Heavy or Bottom Heavy?

Full Cup Bras - Great for those Full on Top or with some Even Fullness

Balcony and Balconette Bras - Great for those Full on top or with some Even Fullness

Half/Demi - Great for those Full on bottom or with some even fullness

Plunge Bra - Great for those Full on bottom or with some even fullness


Bra Style Guide

How do you tell the difference between bras available in our store? Each bra will have a full description with its style (multi-way/multifunction, plunge/push-up, full-cup and/balcony etc) or you can compare the shape to the examples given below:




It's widely known that most women are wearing the wrong size bra. Now you might be surprised to hear that on average women are wearing 1-2 band sizes larger than they need and 2-3 cup sizes smaller than they need!

Now that you know what bra you want, you can start your DIY Bra Sizing. But don’t worry if you don't have a measuring tape. Measuring might feel accurate and is one way of finding a starting point its not the only way due to the sheer variety of body shapes/manufacturer sizes/bra styles. Its our experience that if someone measures themselves with a tape then they can become fixated on the one size that tape provides and to be honest like buying clothes you can be a size 10 in from one shop but a 12 or even dare we say it a 14 in another! Scary! We prefer to take a much more common sense, DIY approach to bra sizing: and all you need is your current bra size, your average dress size and a little bit of trial and error. 



1. Test your band size – Reach around and pull your bra band away from your back – is it loose (more than an inch or so from your back)? If so, your band size is too big. If it’s really loose, subtract two band sizes (always subtract by two, e.g., 38 to 34), if it’s just a little loose, subtract one band size (e.g. 38 to 36). As a rule of thumb your band size should be approximately no more than your dress size plus 20 (dress size 12 + 20 = band size 32).

2. Test your cup size – Feel under your arm for your bra’s underwire. Is the underwire directly below your armpit, or is there breast tissue poking out beyond the underwire? The breast tissue should be fully encased in the underwire without any spillage and without the wires sitting on the breast tissue.
Now check your underwires at the front of the bra – do they lie flat against your skin, or do they stick out? If there is breast tissue beyond the underwire and your underwire isn’t flat, try adding one or two cup sizes (e.g. D to DD or E). If the underwire is only wrong in one place, add one cup size (e.g. D to DD). The central gore should lie flat against the chest with no gaping which can be an issue with the under band size and/or cups being too small.

3. Do the sums – Take your current bra size, do your additions/subtractions from Steps 1 and 2, and that’s your new bra size to test. Don’t panic if your test size sounds too big/weird/no-way-am-I-that-size. Just trust us for now!



Once you’ve got a new bra size to test out, pick your bra and order your new bra. Also you could also order some sizes around the test size, (but remember to adjust the cup and band size, e.g. If picking up a 36C consider a 34D). At we offer FREE RETURNS so don’t worry about returning a bra if it doesn’t fit as you'd expect. Just make sure it's not damaged and the tags are still attached.



Once you have your new bra and a few variants, you’re ready to try them all out. Here is a simple checklist for making sure your new bra fits:

1. Hook the bra on your first (loosest hooks) – This will ensure you are able to get the maximum wear out of the bra once the elasticity starts to go. You need your band to be snug and tight as this is where the majority of the support comes from. Once the bra loses some elasticity then you can try the middle hook and so on as the bra starts to age.

2. Keep your straps relaxed but not loose – too many women rely on the straps for support in their bra, but the band should be giving most of the support, not the straps. Pull out the straps so they sit comfortably but aren’t bearing any real weight, and you’ll get a true idea of how the bra supports you. Put your thumb and finger under strap a lift - if you can pull the strap away from your skin more than an inch tighten the straps accordingly.

3. Make sure the bridge/gore is lying flat on your sternum — poke the piece of fabric between your cups (that’s the bridge/gore), does it lie flat or does your whole bra move when you poke it? If it’s not lying flat, try going up a cup size.

4. Lean over and pull all your breasts in from the side (we call this a swoop and scoop) – this is the part where people start thinking we’re a bit mad! Seriously, it works – lean over so your breasts are pointing to the floor, reach into the cup and pull your breasts into the cup. Now stand back up, and have a good look! If you see a bit of flesh hanging over the top of the cup, that’s a sign that you’re either wearing the wrong style (balcony or half-cup instead of full), or that your cup size is too small.

5. Jump up and down – we call this the Jiggle Test, and it’s great for larger-cup women especially. Do your breasts stay in place when you jiggle up and down a few times? If so, you’re doing well. If your breasts start bouncing like crazy you’ve probably got a band size too large, and if you get a lot of flesh wiggle on the top of your boob, your cup size could be too small, or you should try a fuller cup. Also swivel your body from side to side, try this with you arms in the air. If the band is moving then you need a smaller band, this is often the cause of rubbing and chaffing from the band being able to move around.

6. Put a tight tee-shirt on – we would recommend that you wear a snug, thin little t-shirt when bra fitting, so you can see the shape the bras give you – once you’ve popped the bra on, slip on your t-shirt and check out the general shape/lift. Is there not enough lift? Try a smaller band size (and maybe size up a cup to compensate). Are there lumps and bumps around the cups? If so then try a bigger cup size. Or does the t-shirt have a little dip of fabric at the top of the cup? If so you may need a smaller cup.

7. Try on all of your test bras (the original test size and any variants) and pay attention to how much lift you get, how flat the bridge lies, and how snug your band is against your back. Then, compare these with the bra size you’ve been wearing. With a little trial and error, you should be able to narrow down your size pretty quickly.

8. If none of the bras feel or look right, try a different style of bra with your test sizes and repeat the checklist. Keep experimenting until you feel well-supported! 


WARNING! The hardest type of bra to fit is a t-shirt with molded foam cups as very few breast will be a perfect fit for the preformed cut. 



Bra-sizing isn’t an exact affair – there are simply too many manufacturers, sizing standards, body shapes, and styles for any woman to be one final size. Your “new” size won’t be the same in every brand, and may not even be the same between different styles in the same brand however most brands do tend to ha a couple of base designs. Each season they will bring out other styles but these are still based on that style, so you know that if a 34DD fits you perfectly then it will in these designs too. Its also worth baring in mind that as cup sizes go up some manufacturers skip sizes. At Mysmartypants none of our current suppliers skip sizes and those that come in French or European sizing have already been converted into UK sizing on the site.

The trick is to find a good base size, then adjust that size as required by using the criteria above. This whole process may take a little time, but will be worth it. You can do this process in a one-day blitz, or can simply pay attention to how different bras fit over time and work your size out gradually. Either way, you’ll soon start to learn your size range for your favourite brands and styles, and after a bit more experimentation, you’ll have a whole range of bras that fit you, not a just a bra size!