On a 24kWh LEAF, loss of 1st bar is at approximately 15% capacity loss. The remaining bars each represent approximately 6.25% loss of capacity. The key word here is APPROXIMATELY--there is significant variation which may depend upon on how the car is driven, charged, and stored.
The distance you can drive on a charge depends upon many factors such as speed, temperature, climate control use, and how comfortable you are driving after receiving low battery warning (LBW) and very low battery warning (VLBW). There is significant range hidden below LBW and VLBW--between 15 and 25 miles on my 2015 (was less on 2011). You are in Boston so climate control (heating) could take significant range. Therefore, I recommend either an SV or SL (2013 or newer) to get the advantage of a heat pump. The A/C does not impact range much, but the resistance heater (2013 or newer S and all 2011and 2012 models) can really reduce your range. Even with the heat pump, the resistance heater will be active when the ambient temperature gets colder than the heat pump can handle. You can probably use 70 miles as a base range estimate with moderate climate control use to calculate mileage loss from each capacity bar. To give you an example, I made my daily 52-mile round trip commute with 8 capacity bars showing (4 lost) for a few weeks until Nissan replaced the battery in my 2011. It was during the summer so I used A/C to be comfortably cool and my commute is mostly freeway (carpool lane). I drove several miles after VLBW each evening so there was not much reserve when I got home.
Gerry