Size Chart

Sizes are relative to me, so I will carefully explain...

I am a 5'6" male of 150 pounds with a medium frame, which means I can just touch my fingers around my wrist. My waist fluctuates around 34" (but if you asked I would say 32) and in most respects I am somewhat normal.

Small Someone a bit smaller then me
Medium Fits me like a glove
Large Someone a bit bigger then me

Or for something a bit more scientific try this...
[Compliments of Gordon Carter Custom Tailors]

Chest

Measure around your chest up underneath your armpits and across its maximum point. Measure yourself in a shirt and make sure the tape goes up over your shoulder blades at the back. Measure to the nearest inch.

S 34-36 M 38-40 L 42-44

Jacket Waist

The jacket waist is measured an inch or two higher up than for your trouser waist, around the height of your belly button. Large gentlemen should measure their jacket waist at the widest point, and slim gentlemen at their narrowest. Measure to the nearest 1/2 inch.

S 30-32 M 33-35 L 36-38

Jacket Length

Measure the length of your jacket from your nape of neck down to the length desired. Measure straight down the centre back seam. The proper length should be enough to just completely cover your buttocks. Measure to the nearest 1/2 inch.

S 25-27 M 28-30 L 31-33

Sleeve Length

Measure the length of you jacket sleeve. Measure up from the centre of the cuff up and over to the junction of the arm seam with the shoulder seam. Measure to the nearest 1/4 inch.

S 22-23 M 24-25 L 26-27

Half Back

Measure across the back of your suit jacket between the 2 junctions of the sleeve and armholes. The half back measurement is taken to the nearest 1/8 of an inch, so the full back should be measured to the nearest 1/4 inch. Measure to the whole back to the nearest 1/4 inch and divide by 2.

S 12-14 M 15-17 L 18-20

Pants Waist

Measure around your waistline just above the waistband of your trousers, making sure the tape does not ride over it. Measure to a tightness you would feel comfortable wearing. Measure to the nearest 1/2 inch.

S 30-32 M 33-35 L 36-38

Seat

Measure around your hips and buttocks at their widest point. Make sure you don't have anything in your pockets, otherwise you may get a measure which is too large. Measure to the nearest 1/2 inch.

S 34-36 M 37-39 L 40-42

Inside Leg

Measure the inside leg from your physical crotch down to the bottom of the trouser leg. Make sure you measure down to the same point as for the outside leg. Or, if you have a pair of trousers you know are the correct length for you then measure up along the inside leg seam all the way to the crotch. Measure down to the nearest 1/4 inch.

S 25-27 M 28-30 L 31-33

Thigh

Measure around your thigh at the widest point possible, which should be a couple of inches below the crutch. Make sure you don't have anything large in your pockets which might effect the measure. Measure to the nearest 1/4 inch.

S 18-20 M 21-23 L 24-26

Pants Bottoms

Measure around your trouser bottoms of a trouser you like the cut of. The simplest way is to measure across the width of the bottom when pulled flat and then double the measurement. Measure to the nearest 1/2 inch.

S 14-16 M 17-19 L 20-22