Savings & Growth
Interest Calculator
See what compounding really does over time — including the boost from regular deposits.
Ending balance
$32,063.02
Total deposits
$22,000.00
Total interest
$10,063.02
Growth breakdown
- Principal
- Deposits
- Interest
Year-by-year detail
| Year | Deposits | Interest earned | Balance |
|---|---|---|---|
| 1 | $1,200.00 | $544.62 | $11,744.62 |
| 2 | $1,200.00 | $633.88 | $13,578.50 |
| 3 | $1,200.00 | $727.70 | $15,506.20 |
| 4 | $1,200.00 | $826.33 | $17,532.53 |
| 5 | $1,200.00 | $930.00 | $19,662.53 |
| 6 | $1,200.00 | $1,038.97 | $21,901.51 |
| 7 | $1,200.00 | $1,153.52 | $24,255.03 |
| 8 | $1,200.00 | $1,273.94 | $26,728.96 |
| 9 | $1,200.00 | $1,400.51 | $29,329.47 |
| 10 | $1,200.00 | $1,533.55 | $32,063.02 |
How the interest calculator works
This interest calculator lets you control the two variables that matter most for compound growth beyond rate and time: compounding frequency and contribution schedule. You choose how often interest compounds — annually, semiannually, quarterly, monthly, or daily — and whether recurring deposits land at the start or end of each compounding period. As a savings interest calculator, it's built to mirror how a high-yield savings account or CD actually credits interest; as a compound interest calculator for regular deposits, it also shows how much of your ending balance came from your own deposits versus interest earned on top of them.
Why deposit timing changes your result
Choosing "deposit at start" versus "deposit at end" of each compounding period isn't a cosmetic toggle — it changes how many periods each contribution earns interest for. A deposit made at the start of a period earns that period's interest immediately, while a deposit made at the end waits until the following period to start compounding. Over dozens or hundreds of periods, this timing difference adds up to a measurable gap in the ending balance, even though the contribution amount, rate, and total time are identical. This is also why this doubles as an interest rate calculator for comparing offers: two accounts with the same stated annual rate can produce different real returns purely based on compounding frequency and when deposits are credited.
Daily, monthly, or annual compounding: does it matter?
At the same stated annual rate, more frequent compounding always produces a higher ending balance, but the size of the difference shrinks quickly as frequency increases. Moving from annual to monthly compounding makes a noticeable difference; moving from monthly to daily makes only a small further difference, because each additional compounding period contributes a smaller and smaller slice of extra interest. As a daily compound interest calculator, this tool shows that gap directly — useful for comparing a savings account that compounds daily against one that compounds monthly at a similar advertised rate. In practice, the contribution amount and the rate itself matter far more to your ending balance than compounding frequency alone.
What moves the needle most: rate, time, or contributions?
Of the four inputs on this calculator, time horizon and contribution amount typically swing the ending balance more than small differences in rate or compounding frequency. Doubling how long you let a balance compound roughly doubles or more than doubles the ending growth at a fixed rate, since compounding is exponential rather than linear. Increasing a recurring contribution has an immediate, proportional effect on the deposit side of the balance and a growing effect on the interest side as those larger deposits compound over the remaining years. Rate matters too, especially over long horizons, but for most people starting out, contributing consistently and starting early does more for the ending balance than chasing a marginally higher rate.
Frequently asked questions
What's the difference between simple and compound interest?
Simple interest is calculated only on the original principal, so it grows by the same dollar amount every period. Compound interest is calculated on the principal plus any interest already earned, so the base it's calculated on grows every period — producing accelerating growth over time. This calculator always uses compound interest, since that's how virtually all savings accounts, investments, and loans work in practice.
Should I choose deposit at start or deposit at end?
Match it to reality: if you contribute at the beginning of the month (like a paycheck deposit set up early), choose deposit at start. If your deposit typically clears near the end of the period, choose deposit at end. Deposit-at-start always produces a slightly higher ending balance because each contribution gets one extra period of compounding.
How much does compounding frequency really matter?
Less than most people expect. Switching from annual to monthly compounding at the same rate produces a modest boost; switching from monthly to daily produces only a small additional boost on top of that. The rate itself and how much you contribute have a far larger effect on your ending balance than compounding frequency.
Can I model a CD or fixed-term savings account?
Yes — set the contribution amount to zero, enter the CD's term as the time period, and match the compounding frequency to what the CD discloses (often monthly or daily). The result shows exactly what your lump sum grows to by maturity, before any early-withdrawal penalty.
Does this calculator account for variable interest rates?
No, it assumes a single fixed annual rate for the entire time period. If your rate has changed or you expect it to change, you can run separate calculations for each rate period and add the segments together for a rough blended estimate.
Whether you're comparing savings accounts, sizing up a CD, or just curious how much a recurring deposit habit adds up to, this interest calculator breaks down exactly how much of your balance came from your own deposits versus compounding — period by period, year by year.