The payoff time depends on the balance, the interest rate and how much you pay each month. Because interest is added every month, a fixed payment clears the balance faster than the raw balance divided by the payment suggests only if the payment comfortably exceeds the monthly interest. A free debt payoff calculator runs the month-by-month math for you and shows the payoff date and total interest.
Dividing the balance by your monthly payment ignores the interest that keeps being added, so it always understates the time and cost. The real calculation steps through each month: add that month interest to the balance, subtract your payment, and repeat until the balance reaches zero. That is fiddly by hand, which is why a calculator that reports the exact number of months and the total interest is so useful.
Raising the monthly payment shortens the payoff dramatically because more of each payment goes to principal instead of interest. Paying even a little above the minimum can cut months or years off the timeline. The calculator lets you test a few payment amounts and immediately see how the payoff date and total interest respond.
Because interest is added each month, so part of every payment covers new interest rather than reducing the balance. The simple division ignores that.
The balance drops very slowly and the payoff can take many years. If a payment is below the monthly interest, the balance actually grows.
A lot. Extra payments go straight to principal, which reduces future interest and shortens the payoff, often by more than the extra amount alone would suggest.