Code
Build a size guide
A measuring guide and a chart that answers which size to order.
Fill it in
The measurements per size, as you have them.
What is being sized.
They enter measurements and get a recommendation.
Your prompt
Build a size guide for [your for]. [your sizes] Explain HOW to measure before showing the chart. Most returns come from someone measuring their chest over a jumper or their waist where their trousers sit rather than at the waist, and no chart fixes that. Give both units, and give the garment measurement as well as the body measurement. A shopper who knows the shirt is 108cm around can compare it to a shirt they already own, which is what they actually do. Add a finder: they enter measurements, it recommends a size and says when they are between two and which way to go. Say what the fit is like. "Relaxed, size down if you want it fitted" prevents more returns than any table.
Use Build a size guideOpens with everything above already filled in.
Why this works
Most returns come from someone measuring over a jumper, and no chart fixes that, so this explains how to measure first. It also gives the garment measurement, not just the body one, because shoppers compare against a shirt they already own.