$10,000 at 7% compound interest
Based on a default 10-year period with monthly compounding. Use the calculator below to adjust any input.
Future Value After 10 Years
$20,097
Example
$10,000 invested at 7% compounded monthly for 10 years grows to approximately $20,097 — $10,097 of that is interest earned, on top of your original $10,000.
Total Interest Earned
$10,097
Rule of 72 Doubling Time
10.3 yrs
Exact doubling time at your rate and compounding frequency
9.93 years
Future value, split between principal and interest earned
- Principal: $10,000
- Interest Earned: $10,097
What is Compound Interest?
Compound interest is interest calculated on both the original principal and on the interest already accumulated from prior periods. Unlike simple interest, which only ever earns a return on the original amount, compound interest means your balance earns interest on its own interest — so growth accelerates over time rather than staying flat.
Albert Einstein is widely (if apocryphally) credited with calling compound interest "the eighth wonder of the world" — whoever said it first, the underlying point holds: the earlier money starts compounding, the more dramatic the difference between compound and simple growth becomes, especially over decades-long horizons like retirement savings.
Balance growth over time
Year-by-Year Accumulation Schedule
| Year | Cumulative Interest | Balance |
|---|---|---|
| 0 | $0 | $10,000 |
| 1 | $723 | $10,723 |
| 2 | $1,498 | $11,498 |
| 3 | $2,329 | $12,329 |
| 4 | $3,221 | $13,221 |
| 5 | $4,176 | $14,176 |
| 6 | $5,201 | $15,201 |
| 7 | $6,300 | $16,300 |
| 8 | $7,478 | $17,478 |
| 9 | $8,742 | $18,742 |
| 10 | $10,097 | $20,097 |
Future Value by Compounding Frequency
Every bar uses your exact principal, rate, and term — only the compounding frequency changes. This shows how much difference more frequent compounding actually makes at your numbers.
| Compounding | Future Value | Interest Earned |
|---|---|---|
| Annually | $19,672 | $9,672 |
| Semiannually | $19,898 | $9,898 |
| Quarterly | $20,016 | $10,016 |
| Monthly | $20,097 | $10,097 |
| Daily | $20,136 | $10,136 |
| Continuously | $20,138 | $10,138 |
How Is Compound Interest Calculated?
The standard compound interest formula grows a principal by a periodic rate, repeated
over the total number of compounding periods. When compounding is continuous — a
theoretical limit where interest compounds at every instant rather than at fixed
intervals — the formula switches to Euler's number, e, raised to the rate
times time.
- A — future value (principal + interest)
- P — principal (starting amount)
- r — annual interest rate (as a decimal)
- n — number of times compounded per year
- t — number of years
Why Compounding Frequency Matters
For the same nominal annual rate, compounding more frequently always produces a slightly higher return, because interest is credited — and starts earning its own interest — sooner. The jump from annual to monthly compounding is meaningful; the jump from daily to continuous compounding is nearly imperceptible, since the marginal benefit of compounding even more frequently shrinks quickly. This is why banks advertise APY (which already reflects compounding) rather than only the nominal rate — it lets you compare accounts fairly regardless of how often each one compounds.
The Rule of 72
The Rule of 72 is a mental-math shortcut for estimating how long it takes an investment to double: divide 72 by the annual interest rate. At 6% annual interest, money doubles in roughly 72 ÷ 6 = 12 years. It's an approximation — most accurate for rates between about 6% and 10% — which is why this calculator also shows the exact doubling time solved directly from the compound interest formula for comparison.
Compound Interest Works Both Ways
The same math that grows savings and investments also grows debt. Credit card balances, for example, typically compound daily at high interest rates, which is why carrying a balance can snowball quickly if only minimum payments are made. Understanding compound interest is as useful for managing debt as it is for building wealth — the formula is identical either way, only the direction of the money changes.
Example — Your Current Inputs
$10,000 invested at 7% compounded monthly for 10 years grows to approximately $20,097 — $10,097 of that is interest earned, on top of your original $10,000.
Additional Example — A Classic $1,000 at 5%
$1,000 invested at 5% annual interest, compounded monthly, grows to about $1,647 after 10 years — $647 of that is interest. Compounded only annually instead, the same $1,000 reaches about $1,629, a difference of roughly $18. The gap looks small here because the principal is small; the same percentage gap on a $500,000 portfolio would be about $9,000 — illustrating why compounding frequency matters more as the amount grows.
About These Parameters
- Principal Amount
- The lump sum you start with, before any interest is applied. This calculator assumes a single upfront deposit with no further contributions — for a calculator that also models recurring deposits, see the Interest Calculator or Savings Calculator instead.
- Annual Interest Rate
- The nominal annual rate before compounding is applied. Two accounts quoting the same nominal rate can pay different actual returns depending on how often each one compounds — which is exactly what the frequency comparison table above shows.
- Compounding Frequency
- How often interest is calculated and folded back into the balance. Daily and continuous compounding are common for savings accounts and theoretical modeling; annual or quarterly compounding is more typical for bonds and certain loan products.
Frequently Asked Questions
What's the difference between compound interest and simple interest?
Simple interest is earned only on the original principal every period, so growth is linear. Compound interest is earned on the principal plus all previously accumulated interest, so growth accelerates — the longer the time horizon, the bigger the gap between the two becomes.
Does more frequent compounding always mean a lot more money?
It always means slightly more, but the marginal gain shrinks fast. Going from annual to monthly compounding makes a real difference; going from monthly to daily makes a much smaller one, and daily to continuous is nearly identical in practice.
How accurate is the Rule of 72?
It's a close approximation for annual rates roughly between 6% and 10%, and gets progressively less accurate outside that range. For a precise number at any rate, use the "exact doubling time" figure this calculator solves directly from the compound interest formula.
Why does this calculator not include monthly deposits?
This tool is scoped to the classic, single-lump-sum compound interest formula so the mechanics of compounding frequency and doubling time stay easy to isolate and compare. If you're regularly adding money on top of a starting balance, the Interest Calculator and Savings Calculator both model recurring contributions.