Investment calculator, growth, fees and goals.

An investment calculator shows how a starting amount and regular deposits could grow if they earn a steady return. You give it the starting amount, what you add each month, the years and a return for each year, and it gives back the final balance, what you put in and the growth. This one also takes a yearly fee off the return, shows today’s money after inflation, can take tax off the growth, and can work backward from a goal. The return is a number you type. The page suggests none, names no fund and promises nothing, because real returns go up and down and can be negative.

How to use the investment calculator

1. Under Work out, keep Balance to see where a plan ends. Pick Monthly, Return or Time to start from a goal.
2. Type the Starting amount, what you Add each month, the Years and the Return a year (%).
3. Open Fee, inflation, tax and a deposit rise to type the Yearly fee (%), an inflation rate, a tax rate on the growth and a yearly rise in your monthly amount.
4. Read the cards, the table of lower and higher returns, the chart and the table by year or month.
5. Copy result copies a line of text, Download table (CSV) saves the table and Copy link to these numbers reopens the page with the same inputs.

How the balance is worked out

Each month the balance is multiplied by (1 + net return)^1/12, and then your monthly amount is added. The net return is the return you type minus the yearly fee. A steady 6% return with a 1% fee is a net 5%, so each month multiplies the balance by 1.004074. Take 10,000 to start, 300 a month for 20 years. After the first year the balance is 14,181.77. After 5 years it is 33,106.94. After 20 years it is 148,274.32. You put in 10,000 + 300 × 240 = 82,000, so the growth is 66,274.32.

What a fee costs

Take the fee away and the same plan, at a net 6%, ends at 168,102.94. The 1% fee costs 19,828.62, almost a quarter of the growth the plan would have made without it. A fee looks small as a percentage, but it comes off the whole balance every year, so it costs more the longer the money stays. The page shows this in the card What the fee costs. Use a fee of 0 if you do not pay one. Fund fees and account fees are printed in the fund’s own documents, so type the figure from there.

Lower and higher returns

The table under the cards runs the same plan at a return lower and higher than yours, by the number of points you choose (2 by default). For the example with a 1% fee:

Today’s money is the final balance divided by (1 + inflation) to the power of the years. At 2.5% over 20 years that is 1.6386, so 148,274.32 buys what about 90,487.51 buys now. You choose the inflation rate. For official price data, see the inflation calculator.

Starting from a goal

• Monthly: to reach 500,000 in 25 years from 20,000 at 6% with no fee, add 612.40 a month. At 5% it is 738.00 a month.
• Return: to turn 10,000 plus 300 a month into 150,000 in 20 years you need a return of about 5.09% a year.
• Time: 10,000 plus 300 a month at 6% reaches 100,000 after 168 months, which is 14 years.

A monthly amount that rises each year speeds things up. With 300 rising 3% a year at a steady 6% and no fee, the same 20 years end at 204,769.00 instead of 168,102.94, with 106,733.35 put in instead of 82,000.

What the page leaves out

• Real returns are not steady. A bad year early in the plan can matter more than the average suggests.
• Tax rules differ by country and account. The tax box takes one rate off the growth at the end and nothing else.
• Trading costs, spreads and exchange rates are not included.

For savings accounts and CDs, see the compound interest calculator and the APY calculator. For a retirement plan with a company match, there is the 401(k) calculator.