How to Measure Your Bra Size at Home: A Real Guide

Most people are wearing the wrong bra size, and not by a small margin — the most commonly cited industry estimate is that a majority of women are in the wrong band, cup, or both. The reason isn't carelessness; it's that the actual measurement takes two minutes and almost nobody's shown how to do it properly.

What you actually need

A soft measuring tape and a mirror. No fitting room, no appointment, no guessing from a size you wore years ago — your size changes over time with weight, age, and life stage, so a measurement from even a couple of years ago isn't reliable.

Measuring your band size

Wrap the tape directly under your bust, where a band would sit — snug but not tight, parallel to the floor all the way around, not angled up or down at the back. Round to the nearest whole number. This is your band measurement, and it's the number most people get wrong by guessing rather than measuring, since band fit is about ribcage size, not cup size.

Measuring your cup size

Wrap the tape around the fullest part of your bust, same height as the band measurement, without pulling tight. The difference between this number and your band measurement determines cup size — roughly one inch of difference per cup letter, though this varies slightly by brand and sizing system, which is exactly why "true to size" claims are worth checking against a specific brand's own size chart rather than assuming universal sizing.

Why wireless changes the calculation slightly

Wire-free styles like Kiri's Every Day Bra rely on four-way stretch fabric to hold shape rather than a rigid underwire structure, which means there's genuinely more forgiveness if you're between sizes — sizing down slightly tends to give better support in a wireless style than sizing up, since the stretch fabric fills in the difference more comfortably than excess room does.

When to remeasure

Any significant weight change, a new life stage like pregnancy or postpartum, or simply not having measured in over a year are all reasonable prompts to redo this. Our size guide has the specific band-and-cup ranges mapped to each of our sizes once you have your own measurements in hand.