Factor elevation into estimated mileage used

I would like to know how much kms it's going to take to get somewhere, factoring in gain or loss from elevation. Ie: my destination is 50kms away by distance but there is 1000m in elevation climb between here and there - it's going to take much more than 50kms off my capacity. Or if I reach a peak between and then it's downhill for 600m, I'm going to gain a bunch from regenerative braking. So I'd like to know, while sitting at a charger, that it's going to take 156kms to get there, and so, if I want to get there with 100kms left, I need to charge to about 250kms. Thanks!