Tools
Bra size calculator
Two measurements in, a starting size out. The conversion tables are printed below the form, so the page still answers the question with scripting switched off.
This calculator converts two tape measurements into a band and a cup in British, United States, European and French sizing. It uses the standard arithmetic: the band comes from the underbust measurement, and the cup comes from the difference between the two measurements. Nothing is added to the underbust figure.
Before using it, read how to measure. A tape held badly produces a number no calculator can rescue, and the two most common errors, adding inches to the underbust and letting the tape sag at the back, both produce a size that will not work.
The calculator
Nothing typed into this form is sent anywhere. It runs entirely in the browser and is gone as soon as the page is closed.
Band sizes
The band is the underbust measurement, converted rather than adjusted. European sizing rounds to the nearest five centimetres, British and United States sizing to the nearest even inch, and French sizing is the European number plus fifteen.
| Underbust (cm) | Underbust (in) | United Kingdom and United States | Europe | France |
|---|---|---|---|---|
| 58 to 62 | 23 to 24 | 26 | 60 | 75 |
| 63 to 67 | 25 to 26 | 28 | 65 | 80 |
| 68 to 72 | 27 to 28 | 30 | 70 | 85 |
| 73 to 77 | 29 to 30 | 32 | 75 | 90 |
| 78 to 82 | 31 to 32 | 34 | 80 | 95 |
| 83 to 87 | 33 to 34 | 36 | 85 | 100 |
| 88 to 92 | 35 to 36 | 38 | 90 | 105 |
| 93 to 97 | 37 to 38 | 40 | 95 | 110 |
| 98 to 102 | 39 to 40 | 42 | 100 | 115 |
| 103 to 107 | 41 to 42 | 44 | 105 | 120 |
| 108 to 112 | 43 to 44 | 46 | 110 | 125 |
Cup sizes
The cup is the difference between the overbust and the underbust measurement. British sizing steps roughly every inch, using doubled letters at intervals. United States sizing avoids doubled letters after DD. European and French cups use the same letters as each other and step in two centimetre increments, which is slightly smaller than an inch, so the systems drift apart in the larger sizes.
| Difference (in) | Difference (cm) | United Kingdom | United States | Europe and France |
|---|---|---|---|---|
| 0 | 0 | AA | AA | AA |
| 1 | 2.5 | A | A | A |
| 2 | 5 | B | B | B |
| 3 | 7.5 | C | C | C |
| 4 | 10 | D | D | D |
| 5 | 12.5 | DD | DD | E |
| 6 | 15 | E | DDD | F |
| 7 | 17.5 | F | G | G |
| 8 | 20 | FF | H | H |
| 9 | 22.5 | G | I | I |
| 10 | 25 | GG | J | J |
| 11 | 27.5 | H | K | K |
| 12 | 30 | HH | L | L |
| 13 | 32.5 | J | M | M |
How honest this is
The arithmetic is exact and the result is still only a starting point. Cut, wire width, cup depth and elastic tension vary enough between labels that the same body routinely wears three or four different printed sizes. A calculated size is a hypothesis to test in a fitting room, not a verdict.
- Fasten on the loosest hook. The band should be firm there, with room to tighten later.
- Judge the cup on three things: the top edge, the side under the arm, and whether the centre panel lies flat.
- If the band rides up, go down a band and up a cup. If it digs, go up a band and down a cup. See sister sizing.
- Asymmetry between left and right is normal. Fit the larger side.
- Re measure once a year and after any change in weight. See fit through change.
Does the calculator add anything to the underbust measurement?
No. Adding four or five inches is an old rule that belongs to non stretch band fabric. Applied to a modern band it produces a garment that rides up and cannot support anything.
Why is the result different from the size currently worn?
Most often because the band being worn is too large and the cup too small, which is the classic result of the old adding rule. Try the calculated size before dismissing it.
Does it work without JavaScript?
The form needs scripting, but the two tables above give the same answer by hand. Find the underbust row in the first table and the difference row in the second.