Mathematical calculation for years to reach savings goal
 08-29-2014, 01:12 PM #1 Thinks s/he gets paid by the post   Join Date: Jun 2014 Posts: 1,068 Mathematical calculation for years to reach savings goal I googled and googled and couldn't' find a formula to solve for how long (Years) it takes to reach a savings goal. I wanted this for my retirement Excel spreadsheet. Given current principle, interest, annual contribution, and future value. I found the FV formula... FutureValue= Principal(1+Rate)^Years + Contribution [((1-Rate)^Years)-1]/Rate So I broke out my pen, paper and did the algebra.... Years =Log Base [1+R] of [(C+R*FV)/(R*P+C)] Just posting for anyone who might find it useful for their excel's. __________________
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 08-29-2014, 07:43 PM #2 Recycles dryer sheets   Join Date: Mar 2014 Location: Apex, NC Posts: 183 Why do algebra? Just use Solver in Excel. Or was it the "technical challenge"? __________________
Mathematical calculation for years to reach savings goal
 08-29-2014, 08:24 PM #3 Thinks s/he gets paid by the post   Join Date: Jun 2014 Posts: 1,068 Mathematical calculation for years to reach savings goal I guess i dont know how to use solver. But ya, i was a little proud to break out a logarithm after 15years
 08-30-2014, 06:36 AM #4 Give me a museum and I'll fill it. (Picasso)Give me a forum ...   Join Date: Nov 2010 Location: Vermont & Sarasota, FL Posts: 17,840 Try the NPER function. NPER returns the number of periods for an investment based on periodic, constant payments and a constant interest rate. Input the pv (your current savings) and pmt (annual contributions) as negative numbers and fv (your savings goal) as a positive number and rate (your expected earnings rate per year) and it will return the number of years needed to reach your goal. NPER(rate,pmt,pv,[fv],[type]) __________________ If something cannot endure laughter.... it cannot endure. Patience is the art of concealing your impatience. Slow and steady wins the race. Retired Jan 2012 at age 56...60/35/5 AA

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