The 50/30/20 Budget, Set Up with Smart Flows

The 50/30/20 rule is one of the simplest ways to split a paycheck: half goes to the things you need, 30% to the things you want, and the last 20% to savings. It is easy to remember, and it gives every part of your income a job without a spreadsheet with forty rows.

This tutorial builds the rule in BudgetFlow one flow at a time, with a net salary of 3280 per month. The percentages are typed as math, and a smart flow takes care of the savings part, so the budget keeps working when your income changes.

The Rule in One Table

Needs are the costs you cannot easily skip: rent, groceries, transport and insurance. Wants are everything that makes life nicer but could be cut in a tight month, like eating out, hobbies and subscriptions. Savings covers your emergency fund and long-term investments.

Treat the rule as a starting point that you adapt. If your rent alone eats half of your income, the split will look different, and that is fine. Building it as flows makes it easy to see where the numbers stop fitting.

Step 1: Your Salary Arrives

Create a new budget from the budgets list and open it. Click + Flow, type Salary as From and Main Account as To. Both names are new, so BudgetFlow creates them as you type. Keep the type at Fixed amount, enter 3280 as the amount and pick monthly as the interval.

Step 2: Needs and Wants with Math in Amounts

Now add two more flows from Main Account. The first goes to Needs, and instead of working out half of your salary yourself, type 3280 * 0.5 as the amount. BudgetFlow calculates 1640 and keeps the formula, so you can still see later where the number came from.

The second flow goes to Wants with the amount 3280 * 0.3, which comes to 984. Both flows are fixed and monthly, just like the salary.

At this point Main Account receives 3280 and sends out 2624. The ⚠ next to the budget title points this out: 656 are left over and have nowhere to go. That leftover is exactly the 20% for savings, which is the next step.

Step 3: Let a Smart Flow Handle the 20%

You could type 3280 * 0.2 for savings as well. A smart flow does the job better. Click + Flow, choose Main Account as From and Savings as To, and pick the type Send excess cash. The form shows the sentence "Main Account sends excess cash to Savings", and there is no amount to type.

The smart flow calculates its amount from what is left in Main Account: 3280 minus 1640 minus 984 is 656. That is your 20%, and you never typed it. The ⚠ disappears because nothing is left over anymore.

The real benefit shows when something changes. If you add a small flow from Main Account to a new name, the savings flow shrinks by that amount on its own. You always see what actually reaches your savings, instead of a number that was right three months ago.

Step 4: Fill the Needs Bucket

Needs now holds 1640 per month. Spread it over the real costs with four fixed flows from Needs:

• Rent: 1150
• Groceries: 332
• Transport: 104
• Insurance: 54

Here the budget checks your rule for you. If the needs add up to more than 1640, Needs pays out more than it receives, and the ⚠ next to the title lists it. If they add up to less, the ⚠ shows the leftover cash instead. Either way you notice right away that your needs and the 50% no longer match, and you can decide whether to cut a cost or change the split.

Step 5: Wants, with a Smart Flow for Fun Money

Wants gets the same treatment, with one twist. Add fixed flows from Wants for the things you plan for:

• Eating Out: 260
• Hobbies: 180
• Subscriptions: 47

That is 487 of the 984. For the rest, add a flow from Wants to Fun Money with the type Send excess cash. Fun Money now gets whatever is left in Wants, 497 per month, and it adjusts on its own when a subscription gets more expensive or you cancel one.

Step 6: Split the Savings

The last step decides what happens with the 656 in Savings. A fixed flow of 250 from Savings to Emergency Fund builds your safety net first. Then a second smart flow, from Savings to ETF Portfolio with the type Send excess cash, invests whatever is left: 406 per month.

Switch the interval at the top of the budget to yearly to see the same budget per year. Savings then receives 7872, and 4872 of it goes into the ETF portfolio, which is a more motivating number than 406 per month.

What Happens When Your Salary Changes

Say you get a raise and your net salary goes up to 3500. Click the Salary band in the chart and change the amount. If you also update the two formulas to 3500 * 0.5 and 3500 * 0.3, Needs gets 1750, Wants gets 1050, and the savings smart flow sends 700 to Savings without you touching it.

Your rent did not go up with your raise, though, so Needs now receives 1750 but only pays out 1640. The ⚠ shows the 110 of leftover cash in Needs. You have two good options: plan more for your needs, or add a flow from Needs to Savings with the type Send excess cash, so any money your needs do not use moves on to savings automatically. The second option keeps the budget balanced no matter how your income or your costs change.

Try It with Your Own Numbers

The 50/30/20 rule works best as a first draft. Put your real salary and costs in, look at the chart, and adjust the percentages until they describe how you actually want to live.