The master takes measurements for an individual order, as there are about twenty of them, and you will not be able to do it by yourself.
To determine your approximate size, you just need to take three measurements:

Bust - chest measurement around the fullest part;

Waist - waist circumference at the narrowest place of the waist (take the belt and girth the waist and fix it);

Hips - hip girth at the convex part of the thighs, including the belly bulge.
Compare the result with the size table.

Size table.

Size (UA/RU)	40	42	44	46	48	50	52	54
Bust	80	84	88	92	96	100	104	108
Waist	60	64	68	72	76	80	84,5	89
Hips	86	90	94	98	102	106	110	114

Size (Gr)	40	42	44	46	48	50	52	54
Bust	80	84	88	92	96	100	104	108
Waist	62	66	70	74	78	82	86	92
Hips	86	90	94	98	102	106	110	114