Simple interest
Simple interest is calculated only on the original principal, so growth is linear.
SIMPLE VS COMPOUND
Interest Calculator
Calculate interest and compare simple growth with compound growth.
YOUR INPUTS
Currency changes the display unit (USD) only; amounts are not converted using exchange rates.
COMPOUND RESULT120 months
$16,470.09
Contributing 10% more could add $0.00 to the final value.
A 0.5 percentage-point higher annual rate could add $840.67.
Final balance$16,470.09
Total contributions$10,000.00
Simple-interest balance$15,000.00
Estimated fees$0.00
BALANCE OVER TIME$16,470
YEAR-BY-YEAR
| Period | Final balance | Total contributions | Growth / interest |
|---|---|---|---|
| 12 months | $10,511.62 | $10,000.00 | $511.62 |
| 24 months | $11,049.41 | $10,000.00 | $1,049.41 |
| 36 months | $11,614.72 | $10,000.00 | $1,614.72 |
| 48 months | $12,208.95 | $10,000.00 | $2,208.95 |
| 60 months | $12,833.59 | $10,000.00 | $2,833.59 |
| 72 months | $13,490.18 | $10,000.00 | $3,490.18 |
| 84 months | $14,180.36 | $10,000.00 | $4,180.36 |
| 96 months | $14,905.85 | $10,000.00 | $4,905.85 |
| 108 months | $15,668.47 | $10,000.00 | $5,668.47 |
| 120 months | $16,470.09 | $10,000.00 | $6,470.09 |
Compound interest
Compound interest adds earned interest to the base used for future calculations.
Where each appears
Savings commonly compound. Some short-term lending uses simple interest, but fees and amortization can change real borrowing costs.
NEXT STEP
Keep the same numbers. Answer the next question.
WORKED EXAMPLES
Start with a real number, then change it.
How the Interest Calculator works
Calculations run entirely in your browser. We apply the formulas shown above to a month-by-month schedule, hold your entered rate constant, and treat every result as an estimate—not a forecast or bank quote.
PRIMARY SOURCES
Check the product rules behind the estimate.
These independent government resources provide context. They do not endorse Compound Planner or validate a specific financial product.
FREQUENTLY ASKED QUESTIONS
Clear answers. Better inputs.
Which produces more interest?+
With a positive rate and enough time, compound interest exceeds simple interest on the same principal.
Does frequency matter?+
At the same nominal rate, a higher frequency generally raises the effective annual yield slightly.
Can I use this for loans?+
Only for a rough interest comparison. It does not model payment schedules, fees, or amortization.