50/30/20 Budget Calculator

You move two sliders — wants and savings — and needs is whatever is left over: 100 minus the other two. That is backwards from how a month actually works, and noticing it is the most useful thing this calculator can do for you.

In real life rent is fixed, the car payment is fixed, and groceries have a floor. Needs is the input, not the remainder. So use this in reverse: work out what your needs genuinely cost as a share of take-home, set that first, and see what is actually left to divide. If your needs land at 65%, the calculator will cheerfully show you a 20% savings rate — it just quietly requires wants to fall to 15%, and it will not tell you whether that is a life you would tolerate for a decade.

Take-home, after tax. That distinction moves the answer more than the percentages do. A $75,000 salary is not $6,250 a month to budget with. It is whatever reaches your account after federal and state tax, payroll tax, health premiums, and retirement contributions.

Which raises a question the rule never answers cleanly: does a 401(k) deferral count toward the 20%? If it comes out before you ever see it, your take-home is already net of it, and a strict reading says you need another 20% on top of that. Most people count it, which is defensible. Just be consistent, because it is the difference between claiming a 20% savings rate and actually having a 6% one.

It was built as a sanity check, not a prescription, and it breaks in fairly predictable places. In high cost-of-living areas, when rent alone is 40% of take-home, the framework's only answer is to cut wants to nearly nothing, which is not a plan. With volatile income, freelancers and hourly workers do not have a stable denominator, and percentages of a number that swings 40% month to month do not mean much — budget against your worst recent month instead.

The sharpest failure is high-interest debt. The rule lumps savings and debt payoff into a single 20% bucket, as if they were interchangeable. They are not. A credit card at 24% deserves everything you can throw at it, even at the cost of the wants line, because paying it down is a guaranteed 24% return and nothing in the savings column is going to match that.