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Compound Interest Rate Calculator

Solve for the interest rate that turns one amount into another over a given number of years.

Inputs
Rate resultCalculated
Required rate11.5085% nominal (12.1353% effective)
Formula
i(FV / PV) ^ (1 / N) - 1 per compounding period
Nominal annual rate ri x n
Effective annual rate(1 + i) ^ n - 1
Inputs
  PV  present value         10,000.00
  FV  future value          25,000.00
  t   years                 8
  n   compounding periods   12 (monthly)
Working
FV / PV25,000.00 / 10,000.00 = 2.5
N12 x 8 = 96 periods
i2.5 ^ (1 / 96) - 1 = 0.009590391
r0.009590391 x 12 = 0.11508469
Results
  Rate per compounding period   0.959039%
  Nominal annual rate           11.5085%
  Effective annual rate         12.1353%
  Total growth                  150.000%
  Money gained                  15,000.00
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About the Compound Interest Rate Calculator

Most interest tools run forwards from a rate to a balance. This one runs the other way: given where the money starts, where it needs to end and how long it has, it solves for the rate that makes the two meet. Growing 10,000 into 25,000 over eight years with monthly compounding needs 11.5085 percent nominal, which is 12.1353 percent once compounding is folded in.

The distinction between those two figures is the point of the tool. The nominal rate is what a lender or a product quotes, and it is the periodic rate multiplied by the number of periods. The effective rate is what the money actually does over a year. Both are printed, along with the per period rate carried to six decimal places, so the figure can be pasted into a spreadsheet without rounding drift.

Typical uses are checking whether a savings goal is realistic, reverse engineering the return an investment would have needed, and testing a lender claim. It assumes a single lump sum with nothing added or taken out along the way; if there are regular deposits, no closed form rate exists and a spreadsheet goal seek is the honest approach. When you have the rate and want the balance instead, the Compound Interest Calculator takes it from there.

How to use

  1. Enter the present value, the amount you have now.
  2. Enter the future value you want to reach.
  3. Set the number of years available, using decimals for part years.
  4. Choose the compounding frequency, then read the nominal and effective rates.

Common questions

How do you solve for an interest rate?
Take the ratio of future to present value, raise it to the power of one divided by the total number of periods, subtract one, then multiply by the periods per year for the nominal rate.
Why are two rates shown?
The nominal rate is the quoted figure before compounding, and the effective rate is what a full year of compounding actually delivers. Products advertise the first, your balance follows the second.
Can I include monthly contributions?
No. Adding regular deposits removes the closed form solution, so use a spreadsheet goal seek or the RATE function for that case.
What if the future value is smaller than the present value?
The rate comes out negative, which is the average yearly loss needed to arrive at that lower figure.