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"Rule of 78s" calculation

Does anyone have an example of C# code that does an accurate "Rule of 78s" calculation? I've spent a few hours trying to get this figured out so I can build an amotization table...

I have the table logic built and working. I have spreadsheet values I'm trying to replicate; but I don't understand (and haven't been able to replicate) the fomulas.

Any help here would be greatly appreciated!

Thanks
Payment-Calculator.XLS

TommySzalapski

The "rule of 72" says that if you divide the 72 by the percentage rate, it gives the approximate number of years for the investment to double.

Here is a table showing those values

%      72/%      actual value
1      72      2.047099312
2      36      2.039887344
3      24      2.032794106
4      18      2.025816515
5      14.4      2.018951594
6      12      2.012196472
7      10.3      2.005548375
8      9      1.999004627
9      8      1.992562642
10      7.2      1.98621992
20      3.6      1.927757874
30      2.4      1.876999019
50      1.44      1.792963353

So it's actually pretty close.
The formula for the last column (actual value after 72/P years) is V = (1+P/100)^(72/P)
where P is the percent.

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Miles Thornton

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Thank you Tommy Szalapski!

&quot;Rule of 78s&quot; calculation

"Rule of 78s" calculation