Your waist size if you wear a size 12 depends heavily on the sizing standard (US, UK, or Australian) and the specific brand, but generally falls within the 29 to 33.5 inch (74 to 85 cm) range.
An Australian size 12 is roughly a US size 8, UK size 12, and European size 40, translating to measurements around 97-101cm bust, 78-82cm waist, and 105-109cm hips for women's clothing, often considered a Medium (M). For boys, an AU size 12 fits a 68cm waist and 150cm height, while kids' sizes can vary.
US size 31 jeans fits a 32-inch waist and 43-inch hip and corresponds to a US size 12.
For a healthy measurement you need to aim to be less than: 80cm (31.5in) for all women. 94cm (37in) for most men.
A US women's size 10 typically corresponds to a European size 42 and an Australian size 12, while 32 and 34 refer to inseam/waist measurements in inches for pants, often associated with larger sizes like XL (US 10-12) or 2XL (US 14-16), so it's usually a 32-inch inseam for a size 10, not the waist/hip measurement itself.
In Australia, a size 12 is generally considered a "straight" or "missy" size, falling within average ranges, but due to vanity sizing and inconsistent measurements across brands, it can represent different body sizes; health-wise, a larger waist (over 88cm for women) is a risk factor, and the actual average Australian woman is now closer to a size 16-18, meaning a size 12 is smaller than average, though "fat" is a subjective term related to body image and health metrics like BMI, not just a single number.
(For example: Size 12, XL.)
The "two-finger rule" for pants is a simple fit test: you should be able to comfortably slide two fingers between your waistband and your stomach. It ensures the waist isn't too tight (allowing for bloating or eating) but snug enough to prevent sagging, indicating a good, comfortable fit for both jeans and trousers.
Many women notice an increase in belly fat as they get older even if they don't gain weight. This is likely due to a lower level of estrogen because estrogen seems to have an effect on where fat is located in the body. Genes can contribute to an individual's chances of being overweight or obese too.
A size 32 in jeans typically refers to a 32-inch waist, which often converts to a women's numerical size 12 or 14 (especially in US/AU sizing) or a UK size 14, but it can vary by brand, so always check the specific size chart. For women's clothing, a 32-inch waist usually falls into a size Large or XL range, around a US 12-14 or AU 14.
A combination of things happens as we age. We tend to lose muscle mass, so our abdominal muscles aren't as tight as they once were, and the loss of elastin and collagen in our skin allows gravity to have its way so skin starts to sag. Both can cause the waistline to expand.
To ensure a proper fit, select a belt that is at least 2 inches larger than your pant size (usually the next size up). For example, if you pant size is 34, choose a size 36 belt.
A 90cm belt generally fits a waist size of around 33-34 inches (84-86 cm), often corresponding to a US pant size 32 or 33, but it's best to add a couple of inches to your actual waist measurement for the belt size, or check the specific brand's chart, as the belt measurement is usually from the buckle to the middle hole, not the entire belt length.