Two ways to plan
If you have a deadline, enter the number of months and the calculator gives the monthly deposit needed to reach the goal. If you know what you can afford each month, enter the deposit and the calculator tells you how many months it takes. Both account for interest compounded monthly at the annual rate you enter.
The formulas are the standard future-value equations for a lump sum plus regular deposits. With zero interest they reduce to simple division.
Choosing the interest rate
Use the annual percentage yield your account actually pays. Savings rates change, so treat the result as an estimate and revisit it when rates move. If your money sits in a basic account that pays almost nothing, enter zero.
Interest earned is taxable income in many countries, and the calculator does not deduct tax.
Staying on track
Irregular income makes fixed monthly deposits harder. One approach is to set a percentage of each payment instead. The weekly equivalent figure shows what the monthly deposit looks like at a weekly pace.