CHEST
Measure straight across from armpit seam to armpit seam.
Final size charts belong to the real garment. Use this method to compare a piece you already own.
Lay a well-fitting T-shirt flat without stretching it. Use a soft measuring tape. Record each measurement in centimetres and compare it with the product-specific chart when the collection launches.
Measure straight across from armpit seam to armpit seam.
Measure from the highest shoulder point to the bottom hem.
Measure across the back, from shoulder seam to shoulder seam.
Each official product page should state the intended silhouette, fabric composition, GSM, model height, model size and garment measurements. Those details are not available yet, so no generic size numbers have been invented.