Set a target and see when you get there, or set a date and see what it takes each month. If the target is an emergency fund, size it from what a month actually costs you.
Three to six months of necessary expenses is the usual range — expenses, not income. Put in what a careful month actually costs and pick a multiple; the button sets it as your goal above. How savings accounts work covers where in that range you belong and why.
The rate is treated as an APY, so it compounds monthly at the twelfth root of the annual yield rather than a twelfth of it — using a twelfth would overstate the balance, and the gap widens as the rate rises. Contributions are counted at the end of each month, so nothing earns interest before it arrives. A savings APY is variable and the bank can change it whenever it likes, so a long projection at today's rate is an illustration rather than a forecast. Nothing you type is saved or sent anywhere.
Enter the goal, what you have and what you can add each month. The calculator steps forward a month at a time with interest and tells you when you get there, or what monthly amount lands you there by a date you choose.
APY already includes the effect of compounding within the year, so it is what the account actually earns over twelve months. That is why this calculator treats the rate as an APY and compounds monthly at its twelfth root. How savings accounts work explains why the rate matters more than people expect.
The usual range is three to six months of necessary expenses, meaning expenses rather than income. Where you belong in that range depends on how steady your income is and who depends on it. The emergency-fund panel sizes it from what a careful month costs you.