How do I calculate fuel reserves for IFR and VFR flight plan?

I am trying to figure out how to calculate for IFR and VFR for a flight plan example. So from my basic understanding, VFR means you have to add extra 30 minutes to your fuel reserve, and 45 minutes for IFR. So if I wanted to make a flight plan, would I do distance/speed + .5 (for VFR) or + .75 (for IFR)? For instance, if I am calculating that I need an hour's worth of fuel to go a distance of 100 miles at 100 MPH, how would I figure out how much fuel I'd need taking VFR/IFR into consideration?

• Its not that simple. Its 30 minutes for daytime VFR, or 45 minutes for night time. For IFR, you need to be able to fly to your destination, your alternate, and for 45 minutes beyond that, unless weather is above certain minimums. See 14 CFR 91.167 for IFR and 14 CFR 91.151 for VFR, assuming this is FAA (US regulations). Commented Sep 15, 2016 at 20:58
• And for knowing how much fuel to take into consideration, this is simply looking at the cruise performance charts for that particular aircraft and finding the amount of gallons per hour based on the altitude and power setting. For 30 minutes you take half that value, for 45 minutes you take 75% of that value. You really can't calculate how much fuel you need without knowing how much you are burning. Ground distance really doesn't have anything to do with it, other than calculating how much you need to get from dest->alternate, but you also need to know the wind for that. Commented Sep 15, 2016 at 21:06