As for the direct, object-level questions you make: Yes, it’s very helpful and informative, and I don’t see any major errors. In fact, the “additional funds required” and “extra time to FIRE” charts are very useful, and to my knowledge, haven’t been done before. Congrats!
As for something missing, something I sometimes get requested to calculate is how great is the impact of donating now vs. donating later. Like, what if I want to extra-quickly grow my nest egg for 6-10 years or until 60-80% of the way into FI (amounts to be written-in, of course), before donating? Would that lower my donations much? That is, the reverse of “how much delay for this amount of donations?”.
As general commentary / small things / nitpicks:
On the Savings Rate vs. Donation rate, where the chart measures “years to FI”, I think the caption “Years to reach Financial Independence” should be on top for ease of reading. I found it confusing otherwise, while seeing it on a phone
I think it would be useful to add a knob on cell G109 (Estimated years left living based on average life expectancy), which may be as simple as adding as to let that field be write-in, default like 30 or 40, with a side note on how many years would be based on average life expectancy. That way you can put a “limit option” on how many years you plan on donating, could be useful if less (or more!) than usual expected lifespan.
Extra nitpick: 77 is current average lifespan at birth, and a more useful measure would be expected life expectancy at current age and male/female (see, e.g. https://www.ssa.gov/oact/STATS/table4c6.html,) which for me (male, 40) would be almost 39 extra years, but as you grow older, the difference increases (females at 65 still have almost 20 years left!). If you want to keep it simple (and maybe you should) then write-in, with a note for the 77 years reference, plus a link to the reference actuarial tables, should be simple, yet as precise as the user wants.
I think the graphs below, for donating your nest egg, that currently span until year 2090, should be cut/adjusted to the amount of years in G109, so as not to unnecessarily inflate the y axis. I think a simple =if(J39<=Calculator!$G$109,<formula>,”″) suffices for this (I’ve tested it, and it works for me) (needs to be done on columns K to P on the Chart Data sheet, for the different formulas, and then can be dragged for the whole column)
Extremely helpful commentary. I’ve updated the charts with your recommended formula per comment No. 4, and given some extra commentary around No. 2 and 3. I’ll have to give some more thought to your comments about “donating now vs. donating later” and incorporating this level of flexibility. There’s probably a few ways of doing this -- and perhaps this is best done in a separate section or separate calculator even. It also encourages me think a bit more about audience for this tool—if you are new to giving then my gut tells me something more simple will help someone get onto this path more easily...whereas a tool that is more flexible with more options for donation strategy may be better for someone well versed in this space. I think there is space for both. So again, will think on this one more. Would be very happy to chat with another early retiree directly if you are interested, @Alejandro Ruiz
As for the direct, object-level questions you make: Yes, it’s very helpful and informative, and I don’t see any major errors. In fact, the “additional funds required” and “extra time to FIRE” charts are very useful, and to my knowledge, haven’t been done before. Congrats!
As for something missing, something I sometimes get requested to calculate is how great is the impact of donating now vs. donating later. Like, what if I want to extra-quickly grow my nest egg for 6-10 years or until 60-80% of the way into FI (amounts to be written-in, of course), before donating? Would that lower my donations much? That is, the reverse of “how much delay for this amount of donations?”.
As general commentary / small things / nitpicks:
On the Savings Rate vs. Donation rate, where the chart measures “years to FI”, I think the caption “Years to reach Financial Independence” should be on top for ease of reading. I found it confusing otherwise, while seeing it on a phone
I think it would be useful to add a knob on cell G109 (Estimated years left living based on average life expectancy), which may be as simple as adding as to let that field be write-in, default like 30 or 40, with a side note on how many years would be based on average life expectancy. That way you can put a “limit option” on how many years you plan on donating, could be useful if less (or more!) than usual expected lifespan.
Extra nitpick: 77 is current average lifespan at birth, and a more useful measure would be expected life expectancy at current age and male/female (see, e.g. https://www.ssa.gov/oact/STATS/table4c6.html,) which for me (male, 40) would be almost 39 extra years, but as you grow older, the difference increases (females at 65 still have almost 20 years left!). If you want to keep it simple (and maybe you should) then write-in, with a note for the 77 years reference, plus a link to the reference actuarial tables, should be simple, yet as precise as the user wants.
I think the graphs below, for donating your nest egg, that currently span until year 2090, should be cut/adjusted to the amount of years in G109, so as not to unnecessarily inflate the y axis. I think a simple =if(J39<=Calculator!$G$109,<formula>,”″) suffices for this (I’ve tested it, and it works for me) (needs to be done on columns K to P on the Chart Data sheet, for the different formulas, and then can be dragged for the whole column)
Extremely helpful commentary. I’ve updated the charts with your recommended formula per comment No. 4, and given some extra commentary around No. 2 and 3. I’ll have to give some more thought to your comments about “donating now vs. donating later” and incorporating this level of flexibility. There’s probably a few ways of doing this -- and perhaps this is best done in a separate section or separate calculator even. It also encourages me think a bit more about audience for this tool—if you are new to giving then my gut tells me something more simple will help someone get onto this path more easily...whereas a tool that is more flexible with more options for donation strategy may be better for someone well versed in this space. I think there is space for both. So again, will think on this one more. Would be very happy to chat with another early retiree directly if you are interested, @Alejandro Ruiz