The Prehn Institute
Tool

Compound interest calculator

Enter a starting sum, a regular contribution, an annual rate and a number of years. The calculator shows the final balance and how much of it is contributions and how much is growth.

Result, hypothetical illustration

The figures below are arithmetic output from the rate you entered. They are not a projection, forecast, or representation of any return the Institute or any student has achieved or will achieve.

Future value
$694,709
Total interest
$504,709
Multiplier
3.7×
Time-weighted return
265.64%

Composition

Where the balance comes from.

Contributions total $190,000 across 30 years. The remainder is produced by compounding.

Illustrative only. Rates are assumptions, not forecasts. Nothing here is financial advice.

$190k

Contributions

$505k

Interest

$695k

Balance

Growth over time

The balance, year by year.

Each column is the balance at the end of a year. The gold portion is the money paid in; the blue portion is the growth produced by compounding at the rate entered.

ContributionsInterest
1
5
10
15
20
25
30

Year

Table

The figures in full.

Year-end contributions, interest and balance for every year of the period entered. Figures are rounded to the nearest dollar.

Illustrative only. Rates are assumptions, not forecasts. Nothing here is financial advice.

YearContributionsInterestBalance
1$16,000$955$16,955
2$22,000$2,413$24,413
3$28,000$4,411$32,411
4$34,000$6,986$40,986
5$40,000$10,182$50,182
6$46,000$14,042$60,042
7$52,000$18,614$70,614
8$58,000$23,952$81,952
9$64,000$30,108$94,108
10$70,000$37,144$107,144
11$76,000$45,122$121,122
12$82,000$54,110$136,110
13$88,000$64,182$152,182
14$94,000$75,416$169,416
15$100,000$87,895$187,895
16$106,000$101,710$207,710
17$112,000$116,958$228,958
18$118,000$133,742$251,742
19$124,000$152,173$276,173
20$130,000$172,370$302,370
21$136,000$194,461$330,461
22$142,000$218,582$360,582
23$148,000$244,881$392,881
24$154,000$273,515$427,515
25$160,000$304,653$464,653
26$166,000$338,475$504,475
27$172,000$375,176$547,176
28$178,000$414,964$592,964
29$184,000$458,062$642,062
30$190,000$504,709$694,709