Financial

Compound Interest Calculator

Project growth with compounding and contributions.

Inputs

See how compounding and monthly contributions build over time.

Starting balanceContribution amountAnnual contribution increase (%)Contribution frequencyContribution timingCompounding frequencyInterest rate (annual %)Time horizon (years)Additional months

Start monthStart year

Results

Totals reflect the selected compounding frequency.

Future value

$31,998.32

Total contributions

$22,000.00

Interest earned

$9,998.32

Balance composition

Component	Amount
Starting balance	$10,000.00
Total contributions	$22,000.00
Interest earned	$9,998.32
Ending balance	$31,998.32

Growth schedule

View monthly or yearly balance growth.

Month	Contribution	Interest	Balance
Mar 2026	$100.00	$41.67	$10,141.67
Apr 2026	$100.00	$42.26	$10,283.92
May 2026	$100.00	$42.85	$10,426.77
Jun 2026	$100.00	$43.44	$10,570.22
Jul 2026	$100.00	$44.04	$10,714.26
Aug 2026	$100.00	$44.64	$10,858.90
Sep 2026	$100.00	$45.25	$11,004.15
Oct 2026	$100.00	$45.85	$11,150.00
Nov 2026	$100.00	$46.46	$11,296.46
Dec 2026	$100.00	$47.07	$11,443.53
Jan 2027	$100.00	$47.68	$11,591.21
Feb 2027	$100.00	$48.30	$11,739.50
Mar 2027	$100.00	$48.91	$11,888.42
Apr 2027	$100.00	$49.54	$12,037.95
May 2027	$100.00	$50.16	$12,188.11
Jun 2027	$100.00	$50.78	$12,338.90
Jul 2027	$100.00	$51.41	$12,490.31
Aug 2027	$100.00	$52.04	$12,642.35
Sep 2027	$100.00	$52.68	$12,795.03
Oct 2027	$100.00	$53.31	$12,948.34
Nov 2027	$100.00	$53.95	$13,102.29
Dec 2027	$100.00	$54.59	$13,256.88
Jan 2028	$100.00	$55.24	$13,412.12
Feb 2028	$100.00	$55.88	$13,568.01
Mar 2028	$100.00	$56.53	$13,724.54
Apr 2028	$100.00	$57.19	$13,881.72
May 2028	$100.00	$57.84	$14,039.56
Jun 2028	$100.00	$58.50	$14,198.06
Jul 2028	$100.00	$59.16	$14,357.22
Aug 2028	$100.00	$59.82	$14,517.04
Sep 2028	$100.00	$60.49	$14,677.53
Oct 2028	$100.00	$61.16	$14,838.69
Nov 2028	$100.00	$61.83	$15,000.52
Dec 2028	$100.00	$62.50	$15,163.02
Jan 2029	$100.00	$63.18	$15,326.20
Feb 2029	$100.00	$63.86	$15,490.06
Mar 2029	$100.00	$64.54	$15,654.60
Apr 2029	$100.00	$65.23	$15,819.83
May 2029	$100.00	$65.92	$15,985.74
Jun 2029	$100.00	$66.61	$16,152.35
Jul 2029	$100.00	$67.30	$16,319.65
Aug 2029	$100.00	$68.00	$16,487.65
Sep 2029	$100.00	$68.70	$16,656.35
Oct 2029	$100.00	$69.40	$16,825.75
Nov 2029	$100.00	$70.11	$16,995.86
Dec 2029	$100.00	$70.82	$17,166.67
Jan 2030	$100.00	$71.53	$17,338.20
Feb 2030	$100.00	$72.24	$17,510.44
Mar 2030	$100.00	$72.96	$17,683.40
Apr 2030	$100.00	$73.68	$17,857.08
May 2030	$100.00	$74.40	$18,031.49
Jun 2030	$100.00	$75.13	$18,206.62
Jul 2030	$100.00	$75.86	$18,382.48
Aug 2030	$100.00	$76.59	$18,559.07
Sep 2030	$100.00	$77.33	$18,736.40
Oct 2030	$100.00	$78.07	$18,914.47
Nov 2030	$100.00	$78.81	$19,093.28
Dec 2030	$100.00	$79.56	$19,272.84
Jan 2031	$100.00	$80.30	$19,453.14
Feb 2031	$100.00	$81.05	$19,634.20
Mar 2031	$100.00	$81.81	$19,816.00
Apr 2031	$100.00	$82.57	$19,998.57
May 2031	$100.00	$83.33	$20,181.90
Jun 2031	$100.00	$84.09	$20,365.99
Jul 2031	$100.00	$84.86	$20,550.85
Aug 2031	$100.00	$85.63	$20,736.48
Sep 2031	$100.00	$86.40	$20,922.88
Oct 2031	$100.00	$87.18	$21,110.06
Nov 2031	$100.00	$87.96	$21,298.02
Dec 2031	$100.00	$88.74	$21,486.76
Jan 2032	$100.00	$89.53	$21,676.29
Feb 2032	$100.00	$90.32	$21,866.60
Mar 2032	$100.00	$91.11	$22,057.71
Apr 2032	$100.00	$91.91	$22,249.62
May 2032	$100.00	$92.71	$22,442.33
Jun 2032	$100.00	$93.51	$22,635.84
Jul 2032	$100.00	$94.32	$22,830.15
Aug 2032	$100.00	$95.13	$23,025.28
Sep 2032	$100.00	$95.94	$23,221.22
Oct 2032	$100.00	$96.76	$23,417.97
Nov 2032	$100.00	$97.57	$23,615.55
Dec 2032	$100.00	$98.40	$23,813.95
Jan 2033	$100.00	$99.22	$24,013.17
Feb 2033	$100.00	$100.05	$24,213.23
Mar 2033	$100.00	$100.89	$24,414.11
Apr 2033	$100.00	$101.73	$24,615.84
May 2033	$100.00	$102.57	$24,818.41
Jun 2033	$100.00	$103.41	$25,021.82
Jul 2033	$100.00	$104.26	$25,226.07
Aug 2033	$100.00	$105.11	$25,431.18
Sep 2033	$100.00	$105.96	$25,637.15
Oct 2033	$100.00	$106.82	$25,843.97
Nov 2033	$100.00	$107.68	$26,051.65
Dec 2033	$100.00	$108.55	$26,260.20
Jan 2034	$100.00	$109.42	$26,469.62
Feb 2034	$100.00	$110.29	$26,679.91
Mar 2034	$100.00	$111.17	$26,891.07
Apr 2034	$100.00	$112.05	$27,103.12
May 2034	$100.00	$112.93	$27,316.05
Jun 2034	$100.00	$113.82	$27,529.86
Jul 2034	$100.00	$114.71	$27,744.57
Aug 2034	$100.00	$115.60	$27,960.18
Sep 2034	$100.00	$116.50	$28,176.68
Oct 2034	$100.00	$117.40	$28,394.08
Nov 2034	$100.00	$118.31	$28,612.39
Dec 2034	$100.00	$119.22	$28,831.61
Jan 2035	$100.00	$120.13	$29,051.74
Feb 2035	$100.00	$121.05	$29,272.79
Mar 2035	$100.00	$121.97	$29,494.76
Apr 2035	$100.00	$122.89	$29,717.65
May 2035	$100.00	$123.82	$29,941.47
Jun 2035	$100.00	$124.76	$30,166.23
Jul 2035	$100.00	$125.69	$30,391.92
Aug 2035	$100.00	$126.63	$30,618.56
Sep 2035	$100.00	$127.58	$30,846.13
Oct 2035	$100.00	$128.53	$31,074.66
Nov 2035	$100.00	$129.48	$31,304.14
Dec 2035	$100.00	$130.43	$31,534.57
Jan 2036	$100.00	$131.39	$31,765.96
Feb 2036	$100.00	$132.36	$31,998.32

How this calculator works

Projects account growth with flexible compounding, contribution timing, and contribution frequency. Includes a monthly or yearly schedule and start date selection for timeline planning.

Inputs

Starting balance (principal amount)
Contribution amount and frequency
Annual interest rate
Time horizon in years and months
Compounding frequency (annual, quarterly, monthly, etc.)
Contribution timing (start or end of period)
Start month and year for schedule dates

Outputs

Future value at the end of the period
Total contributions (principal + deposits)
Interest earned above contributions
Monthly or yearly schedule breakdown
Total number of compounding periods

Assumptions

Contributions occur at the end of each month
Rate is constant and compounded at the selected frequency
Taxes, fees, and inflation are not included

Tips

Small rate changes compound significantly over long horizons
Increase contributions to accelerate growth
Use conservative rates for planning

n = years * 12 and r = APR/12

Future Value = P*(1+r)^n + PMT * ((1+r)^n - 1) / r

Total Contributions = P + PMT * n

Interest Earned = Future Value - Total Contributions

Usage examples

Copy a scenario, then tweak inputs to match your case.

Example

Starter investment

Inputs

Starting balance 10,000
Monthly contribution 100
APR 5% for 10 years

Outputs

Future value about 29,000
Interest earned about 7,000

Shows how consistent deposits build over time.

Example

Long horizon plan

Inputs

Starting balance 5,000
Monthly contribution 200
APR 7% for 20 years

Outputs

Future value about 114,000
Interest earned about 61,000

Higher rates and longer horizons magnify compounding.

Yearly balance sample (10,000 + 100/mo at 5%)

Year	Balance	Interest earned
1	11,300	1,300
5	19,000	3,000
10	29,000	7,000

Values are rounded to show growth milestones.

Balance growth by year

YearAccount balance

PositiveNegative

$11,300.00

$19,000.00

$29,000.00

Sample based on 10,000 starting balance and 100 monthly.

Projections are illustrative and not investment advice.

References

Compound interest formula
Future value of an annuity

FAQ

Common questions

What does the Compound Interest Calculator do?

Projects account growth with flexible compounding, contribution timing, and contribution frequency. Includes a monthly or yearly schedule and start date selection for timeline planning. It is part of our financial toolkit.

What inputs do I need?

Typical inputs include Starting balance (principal amount), Contribution amount and frequency, Annual interest rate.

How are the results calculated?

We follow the formulas and assumptions outlined in the "How this calculator works" section. You will see outputs like Future value at the end of the period, Total contributions (principal + deposits), Interest earned above contributions.