Calcs4All

APR 23 · 2026

Investment calculator

Project an investment balance from a starting amount, monthly contributions, annual return, and timing.

What this calculator covers

Use this investment calculator to estimate how a starting balance and monthly contributions can grow over time at a constant annual return.

It lets you choose whether each contribution lands at the beginning or end of the month, which changes how long each deposit has to compound.

The walkthrough keeps the monthly-rate conversion and contribution timing visible so you can compare scenarios without treating the result like a black box.

Frequently asked questions

What does contribution timing mean and does it matter much?
Beginning-of-month contributions are deposited one period earlier than end-of-month contributions, giving each deposit slightly more time to compound. Over long horizons the difference adds up, but for most planning scenarios the gap is modest compared with the effect of the contribution amount or return rate.
Is the annual return a real return or a nominal return?
The calculator uses a nominal annual return — it does not subtract inflation. To estimate real purchasing power growth, you can reduce your return assumption by your expected inflation rate before entering it.
Does this account for taxes or contribution limits?
No. The projection ignores taxes on growth, dividends, and withdrawals, as well as annual account contribution limits. Actual after-tax results will vary based on account type (taxable brokerage, IRA, 401(k)) and individual tax situation.
Why does changing the starting amount have a bigger effect over longer periods?
The starting amount compounds from day one, so it has more time to grow than later contributions do. The further out the projection horizon, the more the initial balance dominates the ending balance relative to new contributions.

Tool

Run the calculation

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yr

RESULT · ENDING BALANCE

â„–073

Primary result

$322,563.78

$15,000.00 with $500.00 added at the beginning of each month and a 7.00% nominal annual return grows to $322,563.78 over 20 years.

Ending balance
$322,563.78
Total contributed
$135,000.00
Growth earned
$187,563.78
Monthly rate
0.5833%

Step-by-step solution

  1. 1.Convert the nominal annual return into a monthly rate: 7.00% ÷ 12 = 0.5833% per month.
  2. 2.Count the full contribution horizon: 20 years = 240 months.
  3. 3.Compound the starting balance and the monthly additions, with contributions landing at the beginning of each month, to reach $322,563.78.

Walkthrough

Visual walkthrough

This projection combines monthly compounding with a recurring contribution stream, and the timing of each deposit changes how long each dollar can grow.

  1. 01

    Translate the annual return into monthly growth

    7.00% ÷ 12 = 0.5833%

    Monthly compounding needs a monthly rate before any growth or contribution math can start.

  2. 02

    Map every contribution month

    240 monthly deposits

    Deposits made at the beginning of each month get slightly different compounding exposure than end-of-month contributions.

  3. 03

    Read the projected ending balance

    The result separates contributed cash from market growth so the projection is easier to audit.

    $322,563.78 projected balance