Because there is no sizing standard for bras, bra pattern sizing will differ from company to company. To further complicate matters, there is no one measurement method to determine what size will work for every body (including the one on my pattern envelope!).

The only reliable way to determine bra size is to try on finished bras made from that pattern! Given the bra sizing challenge, I recommend starting with your ready to wear size – if it fits you well!

I always recommend making a muslin first to test the fit of the bra. This applies not only to new patterns but also to any new fabric you decide to use. I have two posts on how to make muslins (a.k.a. toiles), a fast way and a more thorough way.

If you do not have a ready-to-wear size or at a loss for what size to start with, I offer the below sizing guideline for my bra sewing patterns.

Difference Cup Size
1” A
2” B
3” C
4” D
5” DD or E
6” DDD or F
7” G
8” H
9” I
10” J

MeasuringMeasurement Figure for Orange Lingerie

  • When taking measurements, be sure to stand up straight and exhale fully.
  • Measure body circumference directly under the bust with the tape measure parallel to floor. Round the measurement to the nearest inch, rounding down if you are at the ½” mark. If your measurement is an even number, add 4″, and if it is an odd number, add 5″. This is the band size.
  • Measure body circumference at the fullest part of the bust while wearing a bra that is supportive yet out of a relatively thin fabric. Again, keep the tape measure parallel to the floor.
  • Derive cup size by subtracting the band size from the full bust measurement. Consult the chart below to find cup size. For example, if the full bust is 36″ and the band size is 34″, the difference is 2″. Based on the cup size chart below, this difference corresponds to a B cup. If you are in between sizes, use the larger size.


Sister sizes are bra sizes that have the same bra cup volume and underwire size. The difference between sister sizes is the size of the band. For example, the sizes 30D, 32C, 34B and 36A all have the same cup volume and use the same underwire. The difference between those sizes is the band. This blog post has instructions for how to modify the band to reach the sister sizes on this table

Sister Size Chart for Bra Making #bramaking #brasizing

Orange Lingerie International Bra Size Conversions

SIZE WAIST (Inches) HIP (Inches)
XS 24 – 25 34 ½ – 35 ½”
S 26 – 27 36 ½ – 37 ½
M 28 – 29 38 ½ – 39 ½
L 30 – 32 41 – 42 ½
XL 34 – 36 44 ½ – 46


Underwear patterns are based on a waist and hip measurement.


  • Waist Measurement: Keeping measuring tape parallel to the floor, measure the circumference of the body at the natural waist.
  • Hip Measurement: With feet together and the measuring tape parallel to the floor, measure the circumference of the body at the fullest part of the hips and bottom. This is typically about 9″ down from the natural waist.

Consult the chart to the left to find your size based these measurements.