Investment Calculator - Growth with Monthly Contributions

How the Investment Calculator Works

1. 01Pick a currency and enter your starting lump sum, which can be zero if you are only investing monthly.
2. 02Enter the monthly contribution you plan to add and your expected annual return percentage.
3. 03Set the investment period with the slider, from 1 to 50 years.
4. 04Review the final value, total contributed, and total growth cards, then expand the year-by-year table to see the path.

Projecting Investment Growth Realistically

The calculator compounds monthly: each month it adds your contribution and applies one twelfth of the annual return, the way most brokerage balances actually accrue. The single most important input is the return assumption. Broad stock index funds have historically returned about 7-10% per year over long periods before inflation, bonds closer to 3-5%, and mixed portfolios in between, but any single decade can deviate sharply. A sensible approach is to run three scenarios: pessimistic (4-5%), base (6-7%), and optimistic (9-10%), and plan around the base case. Watch the year-by-year table to see when growth overtakes contributions; with steady investing at 7% that crossover typically happens around year 10-12, and after that point the market is adding more to your balance each year than you are. Remember the projection ignores taxes, fund fees, and inflation. A 1% annual fee reduces a 7% return to 6%, which over 30 years cuts the final balance by roughly a quarter, so check your fund costs before trusting any long-range number.

When to Use the Investment Calculator

Use it before opening a brokerage account, increasing an automatic monthly transfer, or deciding between investing a windfall at once versus spreading it out. It answers concrete planning questions: what does 300 per month become in 25 years, how much difference does starting five years earlier make, and what return do I need to reach a target. It is also useful for explaining compounding to family members with real numbers instead of abstractions.

Common Use Cases

• ·Projecting what a starting sum plus a monthly index-fund contribution grows to over 10, 20, or 30 years.
• ·Comparing scenarios: starting 5 years earlier versus contributing 50% more per month.
• ·Setting a savings target for a house deposit, education fund, or financial independence number.
• ·Showing a partner or family member the long-term effect of a small monthly increase in savings.
• ·Modeling retirement wealth before diving into a full plan with withdrawal rates. → Retirement Calculator
• ·Isolating pure lump-sum growth without monthly additions. → Compound Interest Calculator

Expert Tips

• ✻Time in the market beats contribution size: doubling your horizon usually adds more than doubling your monthly amount.
• ✻Subtract fund fees from your return assumption; a 1% fee on a 7% return removes roughly a quarter of the final balance over 30 years.
• ✻Re-run the projection yearly with your actual balance as the new starting sum to keep the plan honest.

Frequently Asked Questions