How to measure for a waist trainer

You need two numbers. Your waist, measured right above your belly button, sets your size. Your torso length, from the bottom of your ribs to the top of your hip bone, sets the height of the trainer: 8", 10" or 12". Take both with a soft tape, over bare skin, and you're ready to read the size chart.

What you need

• A soft tape measure. No tape? A phone charger cable or a piece of string and a ruler work.
• A mirror, or someone to check the tape is level
• Bare skin or a thin top. Jeans, belts and sweaters add inches that aren't you.

Step 1: measure your waist (your size)

1. Stand up straight and relaxed, feet together.
2. Find your natural waist: the spot right above your belly button. For men, measure around the navel.
3. Wrap the tape around your body at that height. Check in the mirror that it's level all the way around, including at the back.
4. Breathe out normally. Don't suck in.
5. Pull the tape snug, not tight. It should lie flat against your skin without pressing in.
6. Read the number in inches. Take it twice. If the two readings differ, measure a third time and go with the number you get most.

Step 2: measure your torso length (your height)

1. Sit up straight on a chair, feet flat on the floor.
2. Find the bottom of your rib cage at your side.
3. Find the top of your hip bone on the same side.
4. Measure the straight up-and-down distance between them, in inches.

Most women wear the 10". The torso length guide goes deeper, including what to pick if you land right on a line.

No tape measure?

Use a phone charger cable, a shoelace or a piece of string. Wrap it around your waist the same way, pinch the point where it meets, then lay it flat along a ruler or a printed tape. It's slower, but just as accurate if the string doesn't stretch.

Don't use your pant or dress size instead. Clothing sizes change from brand to brand, and most jeans sit below your natural waist. A real measurement is the fastest way to the right size.

Common mistakes

• Measuring over clothes. Even a waistband changes the number. Bare skin or a thin tank only.
• Measuring at your hips or belly. Your size comes from the spot right above your belly button.
• Pulling the tape tight. Snug and flat is right. If it leaves a mark, it's too tight.
• Tape not level. A tape that dips at the back reads bigger than you are. Use a mirror.
• Measuring torso length standing up. Sit up straight. That's when a trainer that's too long starts to dig in.

What to do with your numbers

Your two numbers do two different jobs. Torso length picks the height of the trainer. Your waist picks the size. Here's an example. Say your waist is 30" and your torso is 9.5". Your torso puts you in the 10" Medium. On our women's chart, a 30" waist is a Medium in 10". (In the 12" Long, which is cut a bit smaller, it would be a Large.) So you'd order Active Sculpt or Daily Sculpt in 10", size M.

If you choose a 12" trainer, check again: the 12" length has its own chart. And if you're between two sizes, it depends on whether this is your first trainer. First trainer, go up one. Worn one before, go down one for a firmer hold.

Active Sculpt Waist TrainerFlexible latex for workouts, in 8", 10" and 12". A good first trainer if you train a lot.From $79Shop

Daily Sculpt Waist TrainerOur firmest everyday latex, in 8", 10" and 12". One size chart covers all three lengths. The 12" is cut a bit smaller, so each size fits a waist about 1" smaller in 12".From $79Shop

Got the wrong size anyway? Your first size exchange is free if you request it within 24 hours of delivery. The trainer has to be unworn and unwashed, so try it on gently first. See exchanges and returns.