Budget Buffer Calculator

An emergency fund is meant to cover a genuine financial shock like job loss or a major unplanned expense, typically held in savings and sized in months of expenses. A checking account buffer is smaller and stays in the checking account itself, absorbing the ordinary month-to-month timing mismatches between when income arrives and when bills are due, so the account never dips below zero.

They're self-reported estimates you enter based on how much your income or spending typically swings from month to month, not figures pulled from actual bank transactions. Someone with irregular freelance income or seasonal expenses should enter a higher percentage than someone with a stable salary and predictable bills.

The lower bound only covers whichever single swing — income or expenses — is larger, which works if the two rarely go against you at the same time. The higher bound builds in margin for the less common but costlier case where a low-income month and a high-expense month land together, plus a cushion for variability this model doesn't capture precisely.

No — even without frequent overdrafts, a buffer prevents the stress and juggling of timing bill payments around when a paycheck clears. The overdraft-cost framing in this calculator is a simple way to quantify the benefit in dollar terms, but avoiding the small financial and mental overhead of a tight account balance is a real benefit on its own.