About the Investment Time Calculator
If you know what you have, what you want and the return you expect, the missing piece is time. This calculator finds how many years and months an investment takes to reach a target amount. You can add a deposit each month, and it shows how much of the growth came from your deposits and how much from the return. Type the starting amount, the target, the yearly return and any monthly deposit and the time to reach a target appears at once, with a few related figures underneath, and you can copy the result with one tap. The sums run in your browser, so nothing you enter is uploaded.
Updated October 2026
How to use the Investment Time Calculator
- 1Enter the starting amount, the target, the yearly return and any monthly deposit.
- 2Pick the units or options from the menus if the time to reach a target tool offers them.
- 3Read the time to reach a target in the large result box.
- 4Look at the extra rows for related figures.
- 5Press Copy result to keep the answer.
When you need the time to reach a target
Savers use it to plan for a house, a car or a retirement goal. Students use it to see how fast compound growth works.
A higher return helps, but regular deposits often matter more at the start. The rule of 72 gives a quick guess: divide 72 by the rate to find the years to double.
How the time to reach a target is worked out
Without deposits, years = ln(target ÷ start) ÷ ln(1 + rate). With deposits, the balance is grown month by month at rate ÷ 12 with the deposit added, until it reaches the target. 1,000 growing at 7% a year reaches 2,000 after about 10.2 years, which is 123 months. Adding 100 a month brings the time down sharply.
Every answer on this page comes from that one rule, so you can check any result by hand with a calculator. The figures shown underneath, such as other units, are conversions of the same answer.
- Years and months
- Optional monthly deposits
- Splits deposits from growth
Mistakes to avoid with time to reach a target
A return is never guaranteed, so treat the answer as an estimate. Use a realistic, after-inflation rate to be safe. A zero or negative return with no deposits will never reach a higher target.
On phone and computer
On a phone, type into the boxes one after another and read the time to reach a target underneath; Copy result puts it on the clipboard for a message or a note. On a computer the inputs sit on the left and the answer on the right, so you can change one figure and watch the time to reach a target move. The investment time calculator works the same on both.
Checking your time to reach a target by hand
A good habit is to test the investment time calculator with a case you already know. 1,000 growing at 7% a year reaches 2,000 after about 10.2 years, which is 123 months. Adding 100 a month brings the time down sharply.
If your own figures give a surprising answer, repeat the working yourself: Without deposits, years = ln(target ÷ start) ÷ ln(1 + rate). With deposits, the balance is grown month by month at rate ÷ 12 with the deposit added, until it reaches the target. Small differences usually come from rounding, from mixing units, or from a typing slip in one of the inputs. Time is only one lever, so test the others as well. See the growth with the Compound Interest Calculator, try constant growth with the Continuous Compounding Calculator, and judge your result with the ROI Calculator.
Features
- Returns are not guaranteed
- Use an after-inflation rate
- Zero return never reaches a higher goal
- Clear messages when the time to reach a target inputs make no sense
- Copy the result with one tap
- Private: nothing is uploaded
Frequently asked questions
How do I calculate time to reach a target?
Without deposits, years = ln(target ÷ start) ÷ ln(1 + rate). With deposits, the balance is grown month by month at rate ÷ 12 with the deposit added, until it reaches the target. 1,000 growing at 7% a year reaches 2,000 after about 10.2 years, which is 123 months. Adding 100 a month brings the time down sharply.
What is the formula for time to reach a target?
Without deposits, years = ln(target ÷ start) ÷ ln(1 + rate). With deposits, the balance is grown month by month at rate ÷ 12 with the deposit added, until it reaches the target. The investment time calculator applies it exactly and rounds only the displayed answer to six significant figures.
What is the rule of 72?
Divide 72 by the yearly rate to estimate the years to double.
Does the tool include tax or fees?
No. Lower the return to allow for them.
What if the target is below my start?
Then you are already there, and the tool asks for a higher target.
Is this investment time calculator free and private?
Yes. It is free, needs no account and runs in your browser, so the numbers you type are not uploaded or stored.