How much of your future balance comes from money you add?
Contribute regularly and explore how time, return and payment timing affect accumulation under fixed assumptions.
Change one assumption
Separate money you add from money that grows
The initial investment stays at 100,000 with monthly compounding. Adjust the assumptions below and watch the balance's makeup change.
- Initial principal
- 100,000
- Later contributions
- 600,000
- Investment growth
- 366,390.17
You add 700,000; the remaining 366,390.17 is modeled net growth. A longer horizon gives earlier money more time to compound.
Beginning contributions grow for one extra month. Under these assumptions, the two ending values differ by 5,048.31. The number of contributions stays the same; each payment has more time to grow.
Nominal annual return is divided by 12 for the monthly rate. A constant return is only a scenario, not a prediction; taxes, fees and inflation are excluded.
What did you just see?
Beginning-of-period contributions grow for one more period than end-of-period contributions. Earlier money has more time to compound; a negative assumed return produces investment loss.
Rates, periods and contribution timing
r is the as a decimal. m is contributions and compounding periods per year: 12 monthly, 4 quarterly, 1 yearly. Periodic return i = r / m and n = years × m. b = 1 for beginning contributions and 0 for end contributions. At zero return, ending value is plus all contributions.
Model scope
Assumes constant contributions and return; excludes taxes, fees, inflation and market volatility. It does not predict actual investment outcomes. Inputs and results are calculated in your browser.
Another example
- Enter initial principal 100,000 and contribution 5,000; choose monthly and end of period.
- Set a 7% nominal annual return for ten years; the periodic rate is 7% / 12.
- Compare ending value with 700,000 of total money added; the difference is modeled investment growth.
Show formal definition and formula
Recurring investing adds the same amount at regular intervals. Ending value combines initial principal, later contributions and investment growth; this model assumes a constant nominal annual return.
Convert rate and horizon to periods
Add principal growth and accumulated contributions
At zero return, simply add contributions
Growth is the balance less all money added
Contributions and compounding use the same frequency: monthly 12, quarterly 4, yearly 1. n must be an integer. G is modeled net investment growth and may be negative.
- FV
- Ending value
- G
- Net investment growth; a negative value is a loss
- P
- Initial principal
- A
- Contribution per period
- r
- Nominal annual return as a decimal
- m
- Contribution and compounding periods per year
- t
- Investment years
- i
- Periodic return, equal to r / m
- n
- Contribution periods, equal to m × t
- b
- 1 for beginning contributions; 0 for end contributions
Common mistakes
A constant return is an assumption, not a guarantee. Do not confuse a 5,000 monthly contribution with an annual contribution, or a nominal annual return with an effective annual return.
Frequently asked questions
How do beginning and end contributions differ?
A beginning contribution is added before the period's return and grows for one extra period. With a positive return it produces a higher ending value; at zero return both timings match.
Can I use only principal or only contributions?
Yes. Enter 0 for an absent initial investment or contribution. Use one consistent monetary unit; no currency conversion is performed.
Can the investment period be fractional?
Yes, when it spans whole contribution periods. Monthly contributions for 1.5 years span 18 periods; yearly contributions require whole years. The maximum horizon is 100 years.
You can now explore…
- Separate initial capital, contributions and growth
- Compare contribution schedules and beginning/end timing
Term reference5 terms
Open a term when you need a reminder. Underlined words in the article work too.