Your Chest Size
X Small Small Medium Large X Large
Inches 32 34 36 38 40
cm 81 86 91 96 101
  Under Bust Size*
X Small Small Medium Large X Large
Inches 30 32 34 36 38
cm 70 75 80 85 90

Source: 3rd Rock

*Please note:


  • Are sized by the under-bust elastic size. This is your underbust measurement PLUS 12cm or 5 inches.
  • If your cup size is particularly large but your underbust is not, we suggest one under-bust size larger maximum, as the elastic must not be too loose. 
  • The Aurora bra is suitable for bigger boobs B-D cups.
  • The Saturn is more suitable for A-C cups.

In Our Opinion

The 3rd Rock size chart is accurate and reliable. If you prefer a looser fit and you are between sizes, we recommend choosing the larger size.

We are confident in the fit of 3rd Rock Climbing & Bouldering Garments because:

  • We have tried the t-shirts on ourselves, in a full range of models and sizes.
  • We monitor customer returns.
  • We see customers wearing the t-shirts in our Rock Climbing/Outdoor Shop
  • We have been selling them for years! 

How to Measure Your Chest

Measure Guide
  • Wear just an undergarment or nothing at all.
  • Stand up straight with your arms hanging by your sides
  • Breath normally and run a soft tape measure under your arm pits over the largest part of your chest and across your shoulder blades. The tape measure should be snug, but not tight.


Still not sure what size to get?

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