Ballistics calculators are designed to assist the long range shooter to dial in their scopes. The calculations come from first knowing the speed at which the bullet travels when leaving the barrel (the club has a chronograph for this). This coupled with knowing the calibre and weight of the bullet (in grains) gives you the starting point for the calculator.
There are a huge amount of ballistic calculators available, most of which are available as Apps for your smartphone or tablet.
However, there is still one or two available to use for free online for those of us who don’t have smartphones, or who want to print and laminate (perhaps) the data sheets.
Ive found the JDM free Calculator works extremely well. CLICK HERE TO TRY IT OUT
Simply use the library feature to pick your bullet make (eg Sierra), calibre (eg .224) and weight (eg 69gr). This overides the manual section just below the library. Next put in your velocity (after using a chronograph!) then go to the bottom of the page, tick range metres, leave everything else as it is and press calculate. This then displays a table with your MOA drops in. Use this for the range! (example below). This now gives you your drop at each distance by MOA, use this with your scope turrets as you move out to distance.