In international sizes, plus size is defined as size 1X-4X.
But what do the 1X, 2X, 3X and 4X sizes mean?
Plus Size Clothing
1X = usually slightly larger than XL
2X = usually slightly larger than XXL
3X = XXXL
4X = XXXXL
Bust
Use a flexible measuring tape and measure circumference around body over the fullest part of the bust, while wearing a correct fitting bra.
Waist
Waist: Measure circumference around body at your natural waistline. Your waistline is the narrowest/slimmest part of torso. So make sure to measure at the point where torso is slimmest!
Hips
Measure circumference of the seat at the fullest part of your hips.