You can figure out VAT online. Check this out.
If you want to learn how to deduct VAT using a formula, look here. You'll have to change the formula to reflect 7% or 19%, but this is not a big deal.
If you have a smart phone, you can get a VAT calculator for Android or iPhone. The Android version is free. You have to pay 99 cents for the iPhone version. I just thought I would mention that since my site avatar is... (you can look).