Investment Calculator

Worked example

Example: $5,000 initial investment plus $300/month at 7% for 15 years projects a future value well above the roughly $59,000 contributed. A 1% annual fee meaningfully lowers the ending balance over the same horizon.

How it works

Estimates portfolio growth from an initial amount, monthly contributions, expected annual return, and investment period. An optional annual fee % reduces the net return each month to show fee drag. Shows future value, total contributed, estimated gains, and dollars lost to fees—returns are not guaranteed.

Limitations

Future value math assumes constant rate of return. Does not model taxes, fees, or withdrawal sequences.

Privacy and file handling

Your data stays on your device and is not uploaded.

Accuracy & methodology

This section documents how the calculator works, what it leaves out, and when results were last reviewed. Figures are educational estimates—not professional advice—and are not labeled "current" unless tied to automatically updated reference data.

Formula source or methodology

Compound growth on initial investment with optional periodic contributions at stated return and horizon.

Jurisdiction

General

Unit system

Currency; percent

Rounding method

Currency amounts round to two decimal places (half up via Math.round × 100 / 100).

Assumptions

• Constant return
• Contributions at selected interval

Known omissions

• Not tax, legal, investment, or lending advice. Confirm material decisions with qualified professionals.
• Capital gains tax, dividends, and fees
• Sequence-of-returns risk

Test cases (automated)

• Positive principal yields future value above principal

Version & last verified

Logic version 1.0. Content and formulas last verified 2026-07-24.

Important notice

Results are estimates for educational purposes and are not financial advice. Assumed returns are not guaranteed. Consult a qualified financial professional for personal guidance.