See how savings grow with compound interest and regular contributions. Pick your rate, frequency and term, then watch contributions vs. interest stack up.
Calculator
Projected balance
$18,207.33
Total contributed
$12,000.00
Total interest
$5,207.33
Compounding is building
29%
So far $5,207.33 (29%) of your $18,207.33 balance is growth. The longer it compounds, the bigger that share gets.
How it's calculated
The balance uses the future-value formula A = P(1 + r/n)^(nt) plus the future value of your contributions: FV = PV·(1+i)^N + PMT·[((1+i)^N − 1)/i], where i is the periodic rate (annual ÷ n), N is the total number of periods (years × n), and PMT is the per-period contribution. At a 0% rate the balance is simply your starting amount plus every contribution.
One frequency selector drives both the compounding cadence and the contribution cadence — your contribution is added once per compounding period. "Start of period" contributions (an annuity due) earn one extra period of interest versus "end of period".
Frequently asked questions
Does compounding frequency really matter?
Yes, but less than the rate. The same 10% on $1,000 over a year grows to $1,100 compounded annually and $1,104.71 compounded monthly — about $5 more. Over decades the gap widens, which is why we let you choose annually, semi-annually, quarterly, monthly or daily.
Are my contributions added before or after interest?
That's the contribution-timing toggle. "End of period" (the default) adds the contribution after that period's interest is applied; "start of period" adds it first, so it earns interest for that period too. Start-of-period always ends a little higher.
Is this investment advice?
No. This is an estimate using a single fixed rate. Real returns vary year to year, fees and taxes reduce growth, and inflation lowers what your balance can buy. Treat the result as a what-if, not a guarantee.
How your balance grows
Contributions: $12,000.00 · Interest: $5,207.33
Show data table
How your balance grows
Contributions
Interest
Y1
$100.00
$5.00
Y1
$300.00
$16.58
Y1
$500.00
$30.28
Y1
$700.00
$46.12
Y1
$900.00
$64.12
Y1
$1,100.00
$84.31
Y2
$1,300.00
$106.71
Y2
$1,500.00
$131.34
Y2
$1,700.00
$158.22
Y2
$1,900.00
$187.37
Y2
$2,100.00
$218.82
Y2
$2,300.00
$252.59
Y3
$2,500.00
$288.71
Y3
$2,700.00
$327.19
Y3
$2,900.00
$368.06
Y3
$3,100.00
$411.35
Y3
$3,300.00
$457.08
Y3
$3,500.00
$505.26
Y4
$3,700.00
$555.94
Y4
$3,900.00
$609.13
Y4
$4,100.00
$664.86
Y4
$4,300.00
$723.16
Y4
$4,500.00
$784.04
Y4
$4,700.00
$847.53
Y5
$4,900.00
$913.67
Y5
$5,100.00
$982.48
Y5
$5,300.00
$1,053.98
Y5
$5,500.00
$1,128.21
Y5
$5,700.00
$1,205.18
Y5
$5,900.00
$1,284.93
Y6
$6,100.00
$1,367.48
Y6
$6,300.00
$1,452.87
Y6
$6,500.00
$1,541.12
Y6
$6,700.00
$1,632.25
Y6
$6,900.00
$1,726.31
Y6
$7,100.00
$1,823.31
Y7
$7,300.00
$1,923.29
Y7
$7,500.00
$2,026.28
Y7
$7,700.00
$2,132.31
Y7
$7,900.00
$2,241.40
Y7
$8,100.00
$2,353.60
Y7
$8,300.00
$2,468.92
Y8
$8,500.00
$2,587.40
Y8
$8,700.00
$2,709.08
Y8
$8,900.00
$2,833.98
Y8
$9,100.00
$2,962.14
Y8
$9,300.00
$3,093.58
Y8
$9,500.00
$3,228.36
Y9
$9,700.00
$3,366.48
Y9
$9,900.00
$3,508.00
Y9
$10,100.00
$3,652.94
Y9
$10,300.00
$3,801.34
Y9
$10,500.00
$3,953.23
Y9
$10,700.00
$4,108.65
Y10
$10,900.00
$4,267.63
Y10
$11,100.00
$4,430.21
Y10
$11,300.00
$4,596.42
Y10
$11,500.00
$4,766.31
Y10
$11,700.00
$4,939.91
Y10
$11,900.00
$5,117.25
Y10
$12,000.00
$5,207.33
Results are estimates. Verify with a professional for important decisions.
About this calculator
This calculator shows how a lump sum grows over time when interest compounds and you add regular contributions. Use it to project long-term savings, compare how often interest is applied, or estimate what an investment could be worth at a future date.
How to read your results
The headline figure is your projected ending balance. The stacked-area chart separates the money you put in (contributions) from the interest it earned, so you can see how compounding accelerates growth in the later years. The data table beneath the chart lists the balance at the end of each year.
Worked example
Start with 1,000, add 100 per month at a 6% annual rate compounded monthly for 10 years.
You contribute 13,000 in total, but the balance grows to roughly 18,300 — about 5,300 of that is compound interest the contributions earned.
Frequently asked questions
What is compound interest?
Compound interest is interest calculated on both your original principal and the interest already added to it. Because each period’s interest goes on to earn interest itself, balances grow faster the longer the money stays invested.
How does the compounding frequency change the result?
More frequent compounding (monthly or daily rather than annually) produces a slightly higher balance, because interest is added — and starts earning — sooner. The gap widens with higher rates and longer terms.
Does this account for taxes or inflation?
No. The projection is before taxes and inflation, so your real spending power will be lower than the nominal balance shown. Treat the figure as a gross estimate rather than a guarantee.
How it's calculated
The future value uses the standard compound-interest formula A = P(1 + r/n)^(nt) combined with the future value of a recurring contribution. P is the starting principal, r the annual rate, n the number of compounding periods per year, and t the number of years. Contributions are applied at the start or end of each period depending on your selection.
Spot a translation issue, a calculation issue, or have a suggestion? Let us know.