Measuring your chest takes ninety seconds and prevents most sizing mistakes — which matters, because "chest to fit" is the only number on a size chart that reliably predicts whether a shirt will actually fit. Measure around the fullest part of your chest, under the armpits, tape level and snug rather than tight — then check that number against the specific brand's chart rather than assuming your usual size.
What you need
Almost nothing. A flexible tailor's tape — the soft fabric kind, not a rigid builder's tape, which can't follow your body's curve and gives a wrong number. No tape? Use string and a ruler: wrap it, mark where it meets, measure the string flat. A mirror helps for checking the tape is level, and another person makes it easier, though it's fine alone. Measure over bare skin or a thin shirt — measuring over a hoodie adds inches that don't exist.
Where the tape goes
Precision here is the whole exercise. Wrap the tape around the fullest part of your chest — for most people across the nipple line, running under the armpits and around your back. The tape must sit level all the way round. This is where most people go wrong: the tape rides up at the back where you can't see it. Check the mirror, or run your fingers along it behind you. Stand relaxed and upright, arms at your sides, breathing normally.
The three rules for an accurate number
1. Don't flex, puff, or hold your breath. Measuring an inflated chest gives a number your everyday body doesn't match, and the shirt ends up loose. 2. Level, not tight. Snug enough to stay put, loose enough to slide a finger underneath — pulling tight compresses tissue and under-measures you. 3. Measure twice. Take the reading, remove the tape, reposition, repeat. If the two differ by more than half an inch, something moved.
Chest vs pit-to-pit (the distinction that confuses everyone)
Size charts use both, and mixing them up causes real errors. "Chest to fit" means your body's circumference — what you just measured, and what most apparel charts list. "Garment chest" or "pit to pit" measures the shirt itself, laid flat from armpit to armpit — roughly half the garment's circumference. So a chart listing "chest 20 inches" for a medium is almost certainly a flat garment measurement. Check which you're reading before comparing, or you'll conclude you need a 4XL.
Using your number properly
Two honest points. Sizing isn't standardised between brands — a medium from one label differs meaningfully from another, which is why the measurement matters more than the letter. Always check the specific chart. And consider the fit you want: a fitted fabric like triblend sits close to the body, so most people size up for a relaxed drape, while a boxy heavyweight tee already gives that room. Our size guide lists chest-to-fit figures from the official Bella+Canvas chart. Tracking training progress instead? See full body measurements.
Quick answers
Where do I measure my chest?
Around the fullest part, across the nipple line and under the armpits, tape level all the way round.
Should I flex?
No — stand relaxed and breathe normally.
How tight should the tape be?
Snug but not compressing; you should slip a finger underneath.
No tape measure?
Wrap string, mark it, measure against a ruler.
Chest vs pit-to-pit?
Chest is your body's circumference; pit-to-pit is the garment flat, roughly half that.
Why doesn't my usual size fit everywhere?
Sizing isn't standardised — check each brand's chart.
Size up or down between sizes?
Depends on fabric and cut — fitted fabrics like triblend usually favour sizing up.
The tape rides up at the back where you can't see it. That single thing accounts for most wrong chest measurements.
Measure the fullest part of your chest, under the armpits, tape level and snug, standing relaxed. Take it twice. Then check that number against the specific brand's chart — and confirm whether the chart lists body chest or flat garment measurements, because confusing the two is how people order three sizes too big.