A T-shirt is simple, but the size label still decides whether it clings, hangs or pulls. The most useful single measurement is the chest (or bust). This calculator reads the chest from published charts and shows the size, plus a warning if you sit right at the edge of the next one, which is the situation where the usual advice is to choose the tighter or looser fit.
How to use the T-shirt size calculator
- Choose men’s, unisex or women’s sizing.
- Measure the chest or bust around the fullest part, tape horizontal, under the arms.
- Enter the number in inches or centimetres.
- Read the size and the borderline note. If you are borderline, choose the larger size for a looser fit.
T-shirt size formula (chart lookup)
borderline = upper limit − chest ≤ 0.5 in
EU size from chest girth (cm): 84, 92, 100, 108, 116, 124 for XS to XXL
The ranges are the Nike tops charts (retrieved 2026-10-15), which are body measurements; the EU sizes come from the men’s sports shirt and T-shirt table in Wikipedia’s Clothing sizes article. A chest on the upper limit belongs to that size. Centimetres are inches multiplied by 2.54.
Men’s and unisex (Nike)
| Size | Chest (in) | Chest (cm) |
|---|---|---|
| XXS | 28.1 – 31.5 | 71 – 80 |
| XS | 31.5 – 35 | 80 – 89 |
| S | 35 – 37.5 | 89 – 95 |
| M | 37.5 – 41 | 95 – 104 |
| L | 41 – 44 | 104 – 112 |
| XL | 44 – 48.5 | 112 – 123 |
| XXL | 48.5 – 53.5 | 123 – 136 |
| 3XL | 53.5 – 58 | 136 – 147 |
| 4XL | 58 – 63 | 147 – 160 |
Women’s (Nike)
| Size | Bust (in) | Bust (cm) |
|---|---|---|
| XXS | 27.5 – 29.5 | 70 – 75 |
| XS | 29.5 – 32.5 | 75 – 83 |
| S | 32.5 – 35.5 | 83 – 90 |
| M | 35.5 – 38 | 90 – 97 |
| L | 38 – 41 | 97 – 104 |
| XL | 41 – 44.5 | 104 – 113 |
| XXL | 44.5 – 48.5 | 113 – 123 |
EU sizes by chest girth (Wikipedia)
| International | EU size | Chest girth (cm) |
|---|---|---|
| XS | 36 | 84 |
| S | 37/38 | 92 |
| M | 39/40 | 100 |
| L | 41/42 | 108 |
| XL | 43/44 | 116 |
| XXL | 45/46 | 124 |
Worked example
A man measures a 40 inch chest.
- 40 is above the S limit (37.5) and within M (37.5–41), so the size is M (37.5–41 in).
- In centimetres the chest is 101.6; Wikipedia’s table puts 100 cm at EU 39/40 (M).
- Borderline? no: 41 − 40 = 1 inch from the next size, which is more than the half inch margin.
Fit tips
- Fabric: cotton jersey can shrink a little in the wash, so a very snug fit may become tight.
- Cut: slim, regular and oversized cuts are not on these charts; size up for oversized and down only if the brand says so.
- Length and sleeves: check the product’s measurements, especially shoulder and body length.
- Women’s cut: tapered at the waist; use the women’s chart.
For dress shirts use the Shirt Size Calculator, and for sweatshirts the Hoodie Size Calculator. The result is a guide, not a guarantee of fit for a specific brand.
Sources
Every figure above comes from these pages, read directly on the dates shown. Brand names are used only to identify published charts.
- Nike — men’s tops size chart (chest) — checked 2026-10-15
- Nike — women’s tops size chart (bust) — checked 2026-10-15
- Wikipedia — Clothing sizes (men’s sports shirts and T-shirts by chest girth) — checked 2026-10-15
Frequently asked questions
How do I find my T-shirt size?
Measure around the fullest part of your chest (or bust) with the tape horizontal and look up the number. On Nike’s men’s chart a 40 inch chest is a medium, 44 is the top of a large, and 48.5 is the top of an XL.
What if I am between sizes?
Nike says to order the smaller size for a tighter fit and the larger size for a looser fit. The calculator warns you when your chest is within half an inch of the next size so you can decide.
Is unisex the same as men’s?
Unisex T-shirts usually follow the men’s chart, so the calculator uses it. Women who like a boxier fit often buy a unisex size.
What is the EU T-shirt size?
Wikipedia lists men’s sports shirts and T-shirts by chest girth: XS 84 cm (EU 36), S 92 cm (37/38), M 100 cm (39/40), L 108 cm (41/42), XL 116 cm (43/44) and XXL 124 cm (45/46). The calculator reads the nearest row.
Does the length matter?
Tall T-shirts are longer by about 4.5 cm on Nike’s charts, but chest decides the width. See also Hoodie Size Calculator and Shirt Size Calculator.