Softonic

Investment Calculator

Step 1 / 3 Final value
Next

Enter your starting balance, planned monthly contribution, expected annual return and investment horizon. The calculator estimates the ending balance, total money added and growth from compounding, then helps you sense-check the result against inflation, fees, taxes and market risk.

How the investment calculator works

  1. 1

    Enter the starting balance

    Use your current portfolio value, savings balance or zero if you are modelling a new plan.

  2. 2

    Add the monthly contribution

    Enter the amount you expect to invest each month. Regular deposits are treated as part of the compounding path.

  3. 3

    Choose an annual return

    Use a nominal annual return before inflation. Conservative plans should test lower-return scenarios too.

  4. 4

    Set the time horizon

    Choose the number of years until the goal, such as retirement, a home deposit or a long-term education fund.

  5. 5

    Review the projection

    Compare ending value, total contributions and estimated growth, then adjust the inputs to see how sensitive the plan is.

The maths

For monthly contributions and monthly compounding, the future value can be written as:

FV = PV * (1 + r)^n + PMT * [((1 + r)^n - 1) / r]

Where:

  • PV = present value, or starting balance
  • PMT = contribution per period, monthly in this tool
  • r = periodic rate, annual return divided by 12
  • n = number of periods, years × 12

Why return assumptions matter

Scenario Total contributed Ending balance after 30 years
$500/month, 6% return $180,000 $502,258
$500/month, 8% return $180,000 $745,180
$500/month, 10% return $180,000 $1,130,244
$750/month, 6% return $270,000 $753,387

Over long horizons, a small change in annual return can move the result more than a large change in monthly saving. That is why fees, asset allocation and the difference between nominal and real returns matter so much. A 7% nominal return with 3% inflation is roughly a 4% real return before taxes and fees.

Choosing a realistic rate

  • Stock-heavy long-term portfolio: often modelled around 6-8% nominal in planning examples, but actual returns vary sharply by decade.
  • Balanced stock and bond portfolio: often tested around 4-6% nominal, with lower volatility than an all-equity portfolio.
  • Cash or money market funds: useful for short-term goals, but the real return can be low or negative after inflation.
  • High-inflation environments: use local nominal assumptions and always compare them with expected inflation to understand purchasing power.

Historical return data is a guide, not a promise. Test a low, middle and high case rather than relying on one number.

Common mistakes

  • Forgetting inflation. A future balance can look large while buying less than expected. Use real returns when the goal is purchasing power.
  • Ignoring sequence risk. Two weak market years near the start of withdrawals can damage a plan even if the long-run average return looks fine.
  • Treating taxes and fees as zero. Fund fees, platform costs, dividend taxes and capital gains taxes can reduce the return you actually keep.
  • Locking away every spare dollar. Tax-advantaged or pension accounts can be useful, but keep enough liquid savings for emergencies and near-term goals.

This calculator is for education and planning. It is not financial advice, and it does not guarantee investment results.

Frequently Asked Questions

Use a range. For a long-horizon stock-heavy portfolio, 6-8% nominal is a common planning assumption. For a more conservative portfolio, test 4-6%. Subtract expected inflation if you want a real, purchasing-power projection.

No. The output is before taxes, platform fees and fund expenses. For taxable accounts, pensions or tax-advantaged accounts, adjust the return to reflect the costs and tax treatment that apply to you.

At a 7% nominal rate, monthly compounding gives an effective annual rate of about 7.23%, compared with 7% for annual compounding. Over decades, that difference can noticeably raise the ending balance.

Yes. Run the first phase with monthly contributions, then use that ending balance as the starting balance for a second projection with the monthly contribution set to zero.

Related Tools

BMI Calculator

Calculate body mass index from height and weight. Shows WHO category, healthy-weight range and limitations of BMI.

GPA Calculator

Calculate grade point average from letter grades and credit hours. Supports US 4.0 and 5.0 honors scales with the standard A/B/C/D letter table.

Inflation Calculator

Calculate the equivalent purchasing power of a dollar across any two years using historical CPI data from 1913 to today.

Scientific Calculator

Full scientific calculator with trig, log, exponents, factorial, memory, parentheses and DEG/RAD toggle. Runs in your browser.

Calorie Calculator

Estimate daily calorie needs for your goal using Mifflin-St Jeor BMR and activity factors. Includes deficit and surplus targets.

Binomial Probability Calculator

Compute exact, cumulative and tail probabilities for a binomial distribution. Enter n trials, p success rate and k successes.