Measurements should preferably be taken by another person. Always stand up straight and look straight ahead. BE NATURAL - Relax, and do not inhale and hold your breath or exhale and hold.

CHEST - Measure around the fullest part of the chest (this is generally across the nipple), be sure to keep the tape up under your arms and around shoulder blades. If you will be wearing a thick jumper underneath your jacket or coat, then take the measurements wearing that jumper.
WAIST - Measure the waist keeping one finger between tape and body (The widest point is usually across the navel).
INSIDE LEG - Haggarts shooting or golfing Plus Twos are ¾ length trousers that buckle under the knee giving a "baggy" generous breeks appearance - therefore leg length is irrelevant for Plus Twos. All Haggarts Trousers come with a 36" inside leg length and an unfinished bottom hem to allow for any length adjustment.

Here is a complete set of sizing charts (not all products are available in all sizes - refer to individual product pages) ...