Direct answer
To measure bust for a blouse, wear a thin, unpadded bra, stand straight with your arms relaxed, and wrap a soft tape around the fullest part of the bust, keeping it level at the front and the back. Breathe out naturally, read the number where the tape meets, and repeat once to confirm. That number, together with a waist check, is what a blouse chart row is built on.
What you need, and what to wear
You need only a soft tailor tape, a mirror, and a pen or phone to note the number. A rigid ruler or a construction tape will not wrap the body, and a stretched-out old fabric tape can read long, so check that your tape starts at zero and lies flat. Stand in front of the mirror so you can see the back of the tape as well as the front: most bust measurement errors happen behind you, where a sloping tape goes unnoticed.
Wear the bra you would normally wear under a blouse, ideally thin and unpadded. A padded or push-up bra lifts and adds volume, and the number you get will point to a blouse size that is too large when you wear your usual bra. If you normally wear blouses without a bra, measure that way instead, and note which choice you made, so a later remeasure can be compared fairly.
Stand the way a blouse hangs
Stand straight but relaxed, with your feet a little apart and your arms hanging naturally at your sides. Do not pull your shoulders back sharply or push your chest forward, because a blouse is cut for a normal standing posture, not a posed one. Breathe out gently and stop at the end of a normal breath, rather than holding a deep breath in. Holding your breath can add a fraction of an inch and push you toward the next size row for no real reason.
Ask someone to help if you can, especially for the back of the tape. A helper can keep the tape level across the shoulder blades while you keep your arms relaxed. If you measure alone, bring the tape ends together at the front, then turn slowly in the mirror to check the back line before reading the number.
Find the fullest point first
Before wrapping the tape, find the fullest point of the bust by looking sideways in the mirror. For most people this sits at nipple level, but it varies with shape, and the fullest point is what matters, not a fixed height. Mark it mentally, then wrap the tape around the body at that height. The tape should pass over the fullest point at the front and across the shoulder blades at the back, in one level line all the way round.
Read the number where the tape end meets the tape body, keeping the tape in place while you read. Do not let the tape drop at the back while you lean forward to read the front, or the number will read small. If you are measuring alone, hold the tape with one finger at the meeting point, step back, and read it in the mirror.
How tight is right
The tape should feel firm and secure, like a comfortable bra band, but it should not dig in or flatten the bust. Slide one finger under the tape: it should move with a little resistance, not freely and not with a struggle. If the tape leaves a deep mark when you remove it, you measured too tight, and the number will be smaller than the bust a blouse needs to cover. If the tape slips down when you move your arms, you measured too loose.
Take the measurement twice, and if the two readings differ by more than half an inch, take a third and use the middle value. Small differences are normal, because breathing and posture shift the number slightly. A consistent reading taken twice is far more useful than a single perfect-looking number that you cannot repeat.
Add the waist check
Bust alone sets the blouse size, but waist tells you whether that size will shape well on you. Measure the natural waist, the narrowest point of the torso, usually just above the navel, with the tape level and relaxed. Note it beside the bust number. When you look at a chart, check whether the waist range for your bust row is close to your waist. A large gap between bust row and waist suggests a blouse with adjustable shaping, such as a wrap or a tie waist, may suit you better than a stiff darted blouse.
Hip is worth noting for longer blouses that fall below the waistband. Measure the fullest part of the hip, again with the tape level. For a tucked blouse, hip matters less, but for an untucked hem it decides whether the blouse will pull at the sides. Keep all three numbers together, because a blouse chart works as a set, not as a single figure.
Mistakes that move you a whole size
Measuring over a bulky sweater or a padded bra is the most common error, and it can add two inches or more. Measuring with the tape sloping down at the back is the second: a tape that dips at the back reads long at the front and points to a larger size. Measuring after a large meal or while holding your breath also shifts the number, though usually by less.
Blouse sizing tool
Use the Blouse Size Calculator
Enter bust, waist and hip measurements to estimate a starting blouse size.
Frequently Asked Questions
Where exactly do I measure bust for a blouse?
Measure around the fullest part of the bust, with the tape level all the way round and passing over the shoulder blades at the back.
Should I wear a bra while measuring bust?
Wear the thin, unpadded bra you would normally wear under a blouse, or measure without a bra if you usually wear blouses that way.
How tight should the tape be for a bust measurement?
The tape should be firm enough to stay in place without slipping, but loose enough to breathe normally. It should not compress the bust.
Why does my bust measurement change during the day?
Posture, breathing and the bra you are wearing all shift the number slightly. Measure standing straight, breathing out naturally, and take the reading twice.
Do I need waist and hip measurements too?
Yes, as checks. Bust sets the blouse size, while waist and hip tell you whether the shaping and hem of that size will suit you.