Investment Calculator

This tool projects what an investment becomes when you combine an initial amount, ongoing contributions and an expected annual return. It is built for the planning question rather than the trading question: given the amount you can realistically add each month, what range of outcomes should you expect in ten, twenty or thirty years?

Inputs

Initial investment

Yearly contribution

Expected return(%)

Years

Result

721,034.86

Invested 230,000 · Gains 491,034.86

Visual breakdown

How it works

FV = P(1+r)^t + C × [((1+r)^t − 1) / r]

How the investment calculator works

The engine is the same two-part future value used for savings: lump sum growth plus a contribution annuity, compounded at the periodic rate.

Expected return should be a long-run average, not last year's number. Broad equity indices have historically averaged roughly 7–10% nominal before fees.

Fees compound against you exactly as returns compound for you. A 1% annual fee on a 30-year plan typically removes a fifth or more of the final balance.

Worked example: 10,000 start, 1,000 a month, 8% for 25 years

Lump sum: 10,000 × 1.0066667^300 = 73,400.
Contributions: 1,000 × (1.0066667^300 − 1) ÷ 0.0066667 = 951,000 approximately.
Projected total ≈ 1,024,000 from 310,000 contributed.
Same plan at 7% instead of 8%: about 869,000 — a single percentage point costs 155,000.
Add a 1% annual fee and the effective return drops to 7%, producing exactly that gap.

Common mistakes to avoid

Treating an average return as a yearly return

An 8% average includes years of −20% and +30%. Sequence matters enormously if you are withdrawing, which is why retirement planning needs its own stress test.

Projecting in nominal money and spending in real money

A million in 25 years buys what roughly 470,000 buys today at 3% inflation. Deflate the answer before deciding it is enough.

Ignoring the drag of taxes and expense ratios

Model your net return: gross expected return minus fund costs, platform fees and any annual tax leakage.

Frequently asked questions

What return should I assume?

Use a conservative long-run figure for your asset mix — often 6–8% nominal for equity-heavy portfolios — and run a pessimistic case two points lower.

How long does money take to double?

Divide 72 by the return. At 8% it is about nine years; at 6% about twelve. The rule of 72 calculator does this instantly.

Is it better to increase contributions or chase returns?

Early on, contributions dominate; after fifteen or twenty years, returns dominate. Raising contributions is the part you actually control.

Does this account for market crashes?

No — it applies a smooth average. Treat the output as a central estimate and plan for outcomes 20–30% either side of it.

What is the difference between this and a SIP calculator?

Mechanically they are the same annuity maths; the SIP tool is framed around a pure monthly plan, while this one starts from a lump sum plus contributions.