A bank offers you one deposit at 5% and another at 4.8% compounded monthly. At a glance the first wins, but without the formula you cannot tell how much the ten-year result changes.
How to use Compound Interest Formula step by step
1. Choose what to calculate
Final amount with the classic formula or with FV, with deposits, interest only, continuous compounding, the rate or the years.
2. Fill in amount, rate and years
The rate is typed as a number without the % sign, such as 5, or pointed at a cell that already holds the percentage.
3. Pick how often it compounds
Yearly, twice a year, quarterly, monthly, weekly or daily. Copy the formula and test it against a figure you know.
The Step Count: Traditional Friction vs. KorexTools
Working out compound interest year by year in a table (4 steps)
- Type the starting sum in the first row.
- Multiply by 1.05 in the next row.
- Drag down to year ten.
- Rebuild the whole table when the rate or compounding changes.
With the KorexTools “Compound Interest Formula” builder (3 steps)
- Choose what to calculate.
- Type amount, rate and years.
- Copy a formula that recalculates by itself.
Compounding frequency moves the result more than it seems
The classic formula raises (1 + rate/n) to the power n times years, where n is how many times a year interest is added. The same nominal rate earns more when it compounds monthly than yearly, and the gap widens over time. That is why you fix n before comparing two financial products.
The FV function returns the same figure and accepts regular deposits, with the option of making them at the start or the end of each period. To solve for the other unknown, the rate comes from raising the final amount over the starting sum to one over the years, and the years come from NPER, as long as the rate is divided by the compoundings per year.
Which variant to use
- •A single fixed-term deposit: classic formula or FV without deposits.
- •Saving with a monthly deposit: FV with a payment and a timing type.
- •Finding out what return a goal demands: solve for the rate.
Starting sum 10,000, rate 5% and 10 years
| Compounding | Formula | Final amount |
|---|---|---|
| Yearly | =B1*(1+B2/1)^(1*B3) | 16,288.95 |
| Monthly | =B1*(1+B2/12)^(12*B3) | 16,470.09 |
| Continuous | =B1*EXP(B2*B3) | 16,487.21 |
Common Mistakes and How to Avoid Them
- ⚠️Typing 5 in a cell formatted as a percentage and getting 500%.
- ⚠️Forgetting to multiply the years by the yearly compoundings.
Frequently Asked Questions
Do I type the rate as 5 or as 0.05?
As 5 if you type it into the builder: it divides by 100. If you point at a cell, that cell must hold the percentage already formatted, meaning 5% or 0.05.
What is the difference between the classic formula and FV?
With the same inputs they return the same amount. FV adds regular deposits and returns a negative value unless the starting sum carries a minus sign, which the tool already handles.
How do I find how many years a goal needs?
Choose "Years needed" and enter amount, rate, compounding and the target. The formula uses NPER and divides the outcome by the compoundings per year.
What I would do if I were in your shoes
«Before picking a financial product, run the same scenario with two different rates and compare the end gap, not the bare percentages.» — DataKorex Engineering Team.