Enclosed please find a link to the article describing the technique for strain gauges depositon for various types of measurements as well as the algorithm for relative deformation or strain calculation. https://zetlab.com/en/establishing-bridge-circuits/
For the purpose of load measurements (force or weight) one should take into consideration the tested sample structure — the information of dependence between relative deformation and load is available in corresponding literature.
Otherwise you can use the calibration table — see the «Tension meter» program for the corresponding calculations. You will have to use the reference load for your system and compare the results obtained with the measured values in mV.
LLC «ETMS» Support team