How do you calculate VAT? UKKO.fi administrator September 06, 2017 14:00 Updated Follow The portion of VAT can be calculated as follows: Price (incl. VAT) x tax rate / ( 100 + tax rate)E.g. graphic designer makes a 1000€ invoice in which 24% VAT is included. How many euros is the portion of VAT? 1000 € x 24 / (100 + 24)=1000 € x 24 /124=193,55 € UKKO.fi salary calculator will automatically count the portion of VAT. See also: What does value added tax mean?