What is a budget Sankey diagram?

A chart where each band's width is proportional to an amount of money. Income enters on the left, joins in the middle, and splits on the right into each kind of spending and whatever is left over. Because the widths add up exactly, you can see at a glance which costs take the largest share of your income.

Can a budgeting app make a Sankey diagram for me?

Some can. WealthMode draws one on its Reports page from the transactions you have already categorized, for the last 3, 6 or 12 months, the year so far, or any custom range, and lets you save it as an image.

Should transfers to savings appear in a budget Sankey?

Usually not as spending. Money you move to your own savings or investment account is neither income nor spending, so it belongs in what is left over. Counting it as spending makes the left-over band look smaller than it really is.

Should I make a Sankey for one month or longer?

Longer, if you can. A single month either leaves out yearly costs such as insurance and gifts or exaggerates them in the month they land. Three to twelve months evens those out and shows what your spending usually looks like.

Budget Sankey Diagrams: Draw One by Hand, or Let Your Budget App Do It

Maybe you’ve seen one on Reddit: a chart that starts with a paycheque on the left and fans out into rent, groceries, car and everything else, each band as wide as the money it carries. That’s a Sankey diagram, and a budget is one of the best uses for it. A list of numbers makes you do the comparisons in your head. A Sankey shows them at a glance.

This guide covers how to read one, the counting mistakes that quietly make one wrong, and the two ways to make your own: by hand from a month of estimates, or drawn automatically from your real transactions.

How to read a budget Sankey

A budget Sankey has three columns.

Left: where money came from. Salary, side income, benefits. If you spent more than you earned, a well-built diagram adds a band here for the difference (drawn from savings, or put on a credit card), because that money had to come from somewhere.
Middle: the total. Every source joins into one bar before it splits again.
Right: where it went. One band per kind of spending, plus a band for whatever was left over.

The width of every band is proportional to its amount, so the widths always add up. That’s what makes the chart useful. Three things are worth checking first:

The widest band on the right. For most households it’s housing. If it’s something else, that’s worth knowing.
The left-over band. Its width is your savings rate, in picture form. A thin band means very little is left at the end of the month.
Anything on the left that isn’t income. A shortfall band means spending was higher than income for the period.

The counting mistakes that make a Sankey wrong

A Sankey is only as good as the numbers going into it, and budget numbers are easy to double count. Check these before trusting any diagram, whether you drew it or an app did.

Transfers between your own accounts. Moving $500 from chequing to savings isn’t spending, and it isn’t income when it lands. If it’s counted as either, the diagram shows money flowing where none actually left. It belongs in the left-over band.

Credit card payments. When you buy groceries on a card, the grocery purchase is the spending. The payment you make to the card later is just moving money between your own accounts. Count both and the groceries appear twice.

Refunds. A $120 return should reduce the spending it reverses, not show up as $120 of income.

One month of irregular costs. A single month either leaves out the costs that come once a year (insurance, property tax, holiday gifts) or shows the full amount in the month it lands. Neither is what your spending usually looks like. A diagram over three to twelve months is more honest.

Option 1: Draw one by hand

You need a month of income and spending totals, grouped into six to ten lines. More than that and the bands get too thin to read.

Add up your take-home pay and any other income for the month.
Go through your bank and credit card statements and total the spending by group: housing, groceries, transport, and so on. Leave out transfers to your own accounts and payments to your own credit cards.
Enter the lines into a diagram tool.

Our free Budget Sankey Diagram Maker does this in your browser: enter your lines, and it draws the diagram, adds a shortfall band if spending was higher than income, and folds tiny lines into “Other” so they stay readable. You can download it as an image, and nothing you type is stored.

Drawing by hand works well for a quick picture of a planned budget. Its limits show up when you want to see real spending: step 2 takes an evening with a stack of statements, it’s easy to misfile a transaction or two, and the result is a snapshot you have to rebuild from scratch next month.

Option 2: Let your budgeting app draw it

If your transactions are already categorized in a budgeting app, the hard part of step 2 is done. An app with a Sankey view can draw the diagram from those transactions for any period you pick, and redraw it whenever new transactions come in.

That also fixes the one-month problem: switch the period to six or twelve months and irregular costs even out on their own.

Where WealthMode fits

WealthMode draws this chart on its Reports page, under “Where Your Money Flows”. It’s built from your categorized transactions:

Income categories on the left flow into a single total, which flows out to your spending categories and a Savings band for what was left over.
Transfers between your own accounts are left out, so moving money to savings or paying off your own credit card isn’t counted as spending, as long as the transaction is marked as a transfer.
Refunds are subtracted from the category they came back to, instead of counting as income.
Drawn from savings appears on the left when you spent more than you earned in the period.
Any period: the last 3, 6 or 12 months, the year so far, or a custom range.
Small categories are grouped into “Other” so the chart stays readable.
Share it as an image from the chart’s share button, with or without the amounts.

Transactions can come from automatic bank sync on the Pro plan or from CSV files you download from your bank on the free tier, so you don’t need to connect your bank to see the chart. Budgeting without bank sync explains how the CSV route works, and the Insights feature page shows the chart alongside the rest of Reports.

Budget Sankey diagrams: the short version

A Sankey diagram shows your income and spending as bands whose widths add up, which makes the biggest costs and the size of your leftover obvious at a glance. Leave transfers and credit card payments out of spending, count refunds against what they reverse, and use more than one month if you have irregular costs. Draw one by hand with the free tool for a quick picture, or let a budgeting app draw it from your real transactions so it stays current without the evening of statements.