Account Waterfall

If your four percentages sum to less than 100%, the Remaining figure shows the unallocated dollar amount — money with no assigned destination that you'll want to route somewhere deliberately rather than let disappear into unplanned spending. If they sum to more than 100%, Remaining goes negative, meaning you've committed more of your income than you actually have; both the highlighted Remaining figure and the Remaining bar in the allocation chart go negative so the over-commitment is visible rather than hidden. Total Allocated % shows the raw sum of your four percentages so you can see at a glance whether it's above, at, or below 100%.

Percentage-based allocation automatically scales with your income, so a raise, bonus, or a leaner month for variable income adjusts every bucket's dollar amount proportionally without you needing to rebuild the budget by hand. A fixed-dollar budget can become outdated the moment your income changes, while a percentage waterfall keeps the same underlying priorities intact regardless of how much you're actually bringing in that month.

The classic 50/30/20 rule splits income 50% needs, 30% wants, 20% savings. This calculator's own default (50% bills, 20% savings, 10% investing, 20% discretionary) is a savings-first variation on that rule: savings and investing combined (30%) get a bigger share than discretionary spending (20%), the opposite weighting from the classic rule's 30% wants / 20% savings split. The right split depends heavily on your cost of living, existing debt, and how aggressively you want to save, so treat any starting percentage as a baseline to adjust rather than a fixed rule.

Most versions of this method do prioritize bills and fixed expenses first, since those are typically non-negotiable obligations like rent, utilities, and insurance that must be covered regardless of other goals. Savings and investing are commonly weighted next given their long-term importance, leaving discretionary spending as the most flexible category to adjust up or down when priorities shift.

Revisit your percentages whenever a major change occurs — a raise, a new fixed expense like a mortgage, a change in savings goals, or paying off a debt that frees up cash flow. Outside of major changes, reviewing the split roughly once or twice a year is enough to keep it aligned with your current financial priorities without over-optimizing every month.