ToolVaults

Compound Interest Calculator

Project long-term investment growth with compound interest and regular contributions. Choose your compounding frequency and contribution timing.

Runs 100% in your browser — nothing is uploaded.

Final balance
$300,851
Total contributions
$130,000
Total interest earned
$170,851
Year-by-year
YearBalanceContributionsInterest
0$10,000$10,000$0
1$16,919$16,000$919
2$24,339$22,000$2,339
3$32,294$28,000$4,294
4$40,825$34,000$6,825
5$49,973$40,000$9,973
6$59,782$46,000$13,782
7$70,299$52,000$18,299
8$81,578$58,000$23,578
9$93,671$64,000$29,671
10$106,639$70,000$36,639
11$120,544$76,000$44,544
12$135,455$82,000$53,455
13$151,443$88,000$63,443
14$168,587$94,000$74,587
15$186,971$100,000$86,971
16$206,683$106,000$100,683
17$227,820$112,000$115,820
18$250,486$118,000$132,486
19$274,790$124,000$150,790
20$300,851$130,000$170,851

Frequently asked

What is compound interest?

Interest earned on both the original principal AND on the interest previously earned. It's why "time in the market" beats "timing the market" — small differences in early years compound into large differences over decades.

Does compounding frequency really matter?

Marginally. Going from annual to monthly compounding on 7% for 30 years changes the final balance by less than 1%. Daily vs monthly is basically noise. Focus on the rate and contribution rate instead.

Start-of-period vs end-of-period contributions?

Start-of-period contributes at the beginning of each compounding interval (called "annuity due"), so it earns interest for one extra period. Slightly higher final balance. Most tools default to end-of-period.

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