Quick answer: To measure your inside leg, stand barefoot with your feet slightly apart and run a tape from the top of your inner thigh, at the crotch, straight down to your ankle bone. Most UK retailers use that figure for trousers. UK labels usually show it in inches, so 81 cm is about L32.
Inside leg is the measurement that decides whether trousers pool round your shoes or stop short of them. It is simple to take, but there are two versions in common use, and mixing them up is the main reason people order the wrong length. This guide explains both, shows how to measure on your own or with a helper, and converts the result into UK leg sizes. For other body measurements, start at our body and clothing measurement guides.
What is the inside leg measurement?
Inside leg is the vertical distance from your crotch down the inner leg, usually to the ankle bone. On trousers, the same measurement runs along the inner seam from the crotch seam to the hem, which is why it is also called the inseam.
The European clothing size standard, published in the UK as BS EN 13402-1, defines inside leg length as the distance from the crotch to the soles of the feet, measured in a straight vertical line. That is a body measurement, taken to the floor. Most UK retailers instead ask you to stop at the ankle bone, because that is roughly where a full-length trouser hem sits. ASOS, for example, tells shoppers to measure from the top of the inside leg at the crotch to the ankle bone.
The two figures differ by the height of your ankle bone above the floor, which is several centimetres. Always read the instructions on the size chart you are buying from.
What do you need?
- A soft tape measure, ideally 150 cm (60 in) long with both metric and imperial scales. A steel tape works for the wall method below. See how to read a tape measure if the inch fractions are unfamiliar.
- Close-fitting clothes, such as leggings or underwear. Thick jeans add bulk at the crotch and shorten the reading.
- A helper, if possible. If not, a hardback book and a wall will do.
- A pencil for marking the wall when measuring alone.
How do you measure inside leg with a helper?
- Take your shoes off and stand straight on a hard floor with your feet slightly apart and your weight even on both legs.
- Have your helper hold the end of the tape at the top of your inner thigh, snug against the crotch but not pressed up hard.
- Let the tape hang straight down the inside of one leg. It should be vertical, not following the curve of your thigh or knee.
- Read the tape at the ankle bone (the knobbly bone on the inside of the ankle) for a retailer chart, or at the floor if the chart asks for the full body measurement.
- Measure twice, once on each leg, and use the average. Write it down in both centimetres and inches.
How can you measure your inside leg on your own?
Use a hardback book against a wall to mark your crotch height, then measure from the mark down. It is a method widely used for bike frame sizing, and it is more consistent than trying to hold a tape in place yourself.
- Stand barefoot with your back to a wall and your feet slightly apart.
- Slide a hardback book between your legs, spine upwards, and raise it gently until it meets your crotch. Keep it level and touching the wall.
- Mark the wall at the top of the spine, step away and measure from the mark to the floor. That gives measurement B.
- For measurement A, sit on the floor or a chair, find your inside ankle bone with a finger and measure its height above the floor. Subtract that from B.
Pushing the book up hard gives a longer reading. That suits bike fitting, where the saddle presses up in the same way, but for clothes a gentle contact is closer to how trousers sit. Our guide to bike frame sizing uses the firmer version.
How do you measure inside leg on a pair of trousers?
Lay trousers that fit you well flat, then measure along the inner seam from the crotch seam to the bottom of the hem. This is often the most useful figure of all, because it already includes your preference for where the hem should fall.
Smooth the legs so the seams lie flat, without stretching the fabric. If the trousers are cropped or deliberately long, take that into account: an ankle-grazer measured this way will undersize a full-length pair.
What are the standard UK leg lengths?
There is no single UK standard, but short, regular and long fittings usually step up in 2 in (about 5 cm) increments. The examples below come from two UK retailers’ own size guides and show how much they vary.
| Retailer and range | Leg fitting | Inside leg (inches) | Inside leg (cm) |
|---|---|---|---|
| ASOS men’s jeans and trousers | Short | 30 in | 76 cm |
| ASOS men’s jeans and trousers | Regular | 32 in | 81 cm |
| ASOS men’s jeans and trousers | Long | 34 in | 86 cm |
| Hobbs women’s | Petite | 30 in | 76 cm |
| Hobbs women’s | Standard | 31 in | 79 cm |
Both retailers describe these as guides, and individual styles can differ. A wide-leg or bootcut trouser is often cut longer than a slim one in the same labelled length, so check the product page for a garment measurement when one is given.
How do you convert inside leg from cm to inches?
Divide centimetres by 2.54 to get inches, or multiply inches by 2.54 to get centimetres. One inch is exactly 2.54 cm, so an 81 cm inside leg is 31.9 in, which you would round to L32.
| Label (inches) | Centimetres | Label (inches) | Centimetres |
|---|---|---|---|
| 26 in | 66.04 cm | 32 in | 81.28 cm |
| 27 in | 68.58 cm | 33 in | 83.82 cm |
| 28 in | 71.12 cm | 34 in | 86.36 cm |
| 29 in | 73.66 cm | 35 in | 88.90 cm |
| 30 in | 76.20 cm | 36 in | 91.44 cm |
| 31 in | 78.74 cm | 37 in | 93.98 cm |
For any other value, our cm to inches converter gives the exact figure.
Which leg length should you choose if you are between sizes?
For full-length trousers, choose the longer size and have them shortened if needed. Taking up a hem is a simple alteration, while letting one down depends on how much spare fabric is folded inside, which is often very little.
Think about the shoes you will wear, too. Trousers for heeled boots or formal shoes are usually worn a little longer than those for trainers. If you are being measured for tailoring, the fitter will set the hem with your shoes on; our guide to measuring for a suit covers that in more detail. For the outside length from waistband to hem, see how to measure trouser length.
Common mistakes to avoid
- Measuring in shoes. Heels lift the ankle bone and change the result. Always measure barefoot.
- Following the leg’s curve. The tape should hang straight, not wrap round the knee or thigh.
- Mixing up the two definitions. A crotch-to-floor figure used on a crotch-to-ankle chart can push you a size or more too long.
- Confusing inside leg with outside leg. Outside leg runs from the waistband down the outer seam and is much longer.
- Measuring over thick fabric. Denim seams at the crotch stop the tape sitting high enough and make the leg look shorter.
Frequently asked questions
Where do you measure inside leg from and to?
From the crotch at the top of the inner thigh, straight down to the ankle bone for most UK trouser charts. Some charts, and the BS EN 13402-1 standard, measure all the way to the floor.
Is inside leg the same as inseam?
Yes. Inseam is the term more common in the US for the inner leg seam on trousers. On a garment, both mean the length from the crotch seam to the hem.
What does L32 mean on jeans?
L32 means a 32 in inside leg, which is 81.28 cm. The W number on the same label is the waist size in inches.
What is a regular leg length in the UK?
It varies by retailer. ASOS lists a regular men’s leg as 32 in (81 cm), while Hobbs gives a standard women’s inside leg of 79 cm (31 in).
Can I measure my inside leg without help?
Yes. Stand against a wall, raise a hardback book gently to your crotch, mark the wall at the top of the spine and measure from the mark to the floor.
Sources
- BSI: BS EN 13402-1 Size designation of clothes: definitions of body measurements, including inside leg length.
- ASOS men’s jeans and trousers size guide: short, regular and long leg lengths and measuring instructions.
- Hobbs size guide: women’s standard and petite inside leg measurements.
- National Physical Laboratory: the inch is defined as exactly 25.4 mm.