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Savings "What Will It Be Worth" Calculator

Project what a starting balance plus regular monthly deposits will grow to, with compound interest — and see how much is your money versus earned interest.

Starting balance

Monthly deposit

Annual interest rate

Years to save

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How it works

Future value = start × (1 + i)^n + deposit × ((1 + i)^n − 1) ÷ i, where i = annual rate ÷ 12 and n = years × 12 (i = 0 → start + deposit × n)

This is the future-value formula for a lump sum plus a stream of regular deposits, compounded monthly. The starting balance grows on its own while each monthly deposit compounds for the time it stays invested, so early contributions do far more work than late ones. Separating the total into "money you put in" and "interest earned" makes compounding visible: over long horizons the interest can rival or exceed everything you deposited.

Worked example

Start with $5,000, add $300 a month at 5% for 10 years (n = 120 months, i = 0.4167% monthly). The balance grows to about $54,820. You contributed $5,000 + $36,000 = $41,000, so roughly $13,820 is compound interest earned along the way.

Frequently asked questions

Does this assume interest compounds monthly?

Yes. It uses monthly compounding on both the starting balance and each deposit, which matches how most savings accounts and many investment plans credit growth. Annual compounding would give a slightly lower figure at the same stated rate.

Is the result in today's dollars?

No — it is the nominal future balance. To see its purchasing power, run the result through an inflation calculator, since prices will also rise over the same period.

What rate should I assume?

Use the actual APY for a savings account, or a conservative long-run return for investments (many planners use 5–7% for a diversified portfolio). Higher assumed rates compound dramatically over long horizons, so err on the cautious side.

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Educational estimate only, not insurance, tax or financial advice. Real premiums, contribution limits and costs depend on your carrier, plan, state and personal circumstances — get a quote and check current IRS limits.