One of the reasons jacket fits and styles are so hard to describe is they cannot easily be put into numbers.

Trousers, by comparison, are pretty straightforward.

From the shoe up, there is: circumference at the trouser opening or bottom, at the knee, and then at the fork or thigh.

There might be subtle variations in between these (particularly from iron work), but in general you can draw a straight line from one to the other, and describe the line of the leg.

Above the fork there is the circumference at the seat (bum) and then the waist. These are more a case of comfort and fit rather than style.

And above the waist there is the height of the trouser – usually described as the rise, from the fork to the top of the waistband.

In this post – in response to reader requests – I’ll set out what I usually choose in terms of those first three measurements (bottom, knee, thigh), in order to describe the style of the trousers. Rise can be left for another day.

I checked four types of trouser I have and have covered on the site, in preparation for this post:

• My Whitcomb & Shaftesbury tailored trousers (covered recently here)
• My Cerrato tailored trousers (a decent proxy for all the Italian trousers I have)
• My ready-made Incotex chinos (my go-to chino, their classic fit)
• My bespoke Levi’s jeans (slimmer than some of my jeans, but still a decent proxy)

Interestingly, although these go from very formal trousers to very casual, there wasn’t much variation except in the denim.

The average was the Whitcomb & Shaftesbury trouser (above), which measured:

• Bottom: 19cm (7.5 inch, diameter)
• Knee: 24cm
• Thigh: 32cm

Cerrato (shown top) was also 19cm at the bottom, but a little narrower at the knee and thigh, by half a centimetre each time.

So Marco clearly cuts a little closer to the thigh, going in a little more sharply under the seat before running down through the leg.

Interestingly, it is this part of the cut, at the thigh, that I think often determines whether a trouser looks old-fashioned or old-mannish. You can have a wide-legged, swinging Oxford bag, but if it is cut relatively close here, it avoids the old comfort-oriented look.  

Of course, the further you go up the leg, the less room there is for style, and the more is constrained by your actual legs and by comfort.

The bottom of the trouser could be narrowed by 2cm and still fit OK; but if the thigh was 2cm narrower, it would be very restrictive when you sat down.

(The Pommella trousers, shown above, are perhaps the narrowest I have in this respect.)

My Incotex chinos (above) were actually slightly wider at the bottom, at 19.5cm, which is not what I was expecting. But they had less taper than the others, with the knee measurement at 23.5cm.

My Levi’s (below) were the only ones that were substantially narrower. The bottom here was 17.5cm, and the knee 21cm.

A narrower leg can be better suited to casual trousers like jeans, where elegance and straight, clean lines are less of a priority.

And narrower trousers do tend to look slightly younger – an association that is of course highly relative, dependent on social context, and changes over time; but still cannot be ignored.

That said, today I would have my jeans slightly wider; a new pair are being cut with an opening of 18 cm.

All this will hopefully be useful to those many readers that asked about what to say when their tailor asks about such things.

But it must be remembered that these measurements are also relative to the customer.

We’ve already noted how little room there is for variation in the thigh, but even at the bottom of the trouser, the opening needs to be in proportion.

A man with a very big waist (mine measures 33 inches, or 84cm) will look silly if his trouser tapers aggressively to a 16cm opening. He will need a slightly wider leg.

And a taller man can arguably also get away with more taper, as there is more leg in which to do it.

Shoe size is also often used as a reference for how wide the leg opening should be.

Personally I think this is over-emphasised, as the correlation between shoe size and height or weight is not that strong, and those two things are more important.

There are other variables, of course, such as the rise of the trouser, where a man tends to carry his weight, and so on. These together make it impossible to create a calculation that spits out an optimum leg line.

Tailors often have rules to go by – such as the knee being two inches bigger than the bottom – but these are rough guides and are expected to change at the first fitting, when both tailor and customer look at how they like the overall shape. 

I would encourage readers to do that too, and only use my measurements as a single reference point, entirely dependent on my physical measurements. 

I am, since you ask, just over 6 foot tall (183cm), measure 33 inches around the waist, and hover around 12 stone (76kg).

A bit personal, but I’ll allow it.