accounting equation
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Think of everything a business has — cash, equipment, inventory, money owed to it. Now ask a simple question about every dollar of it: where did that dollar come from? There are only two possible sources. Either someone outside lent it (so the business owes them), or the owners put it in or the business earned and kept it (so it belongs to the owners). That observation is the whole idea behind the accounting equation.
The accounting equation states: Assets = Liabilities + Equity. Assets are what the business owns or controls; liabilities are what it owes to outsiders; equity is the owners' residual claim — what would be left for them if every asset were sold and every debt paid. The equation must always balance, because the two sides are simply two views of the same pile of resources: the left side lists the resources, and the right side lists who has a claim on them. Rearranged, it also says Equity = Assets − Liabilities, which is why equity is called the residual. For example, a business with 100,000 dollars of assets and 60,000 dollars of liabilities has 40,000 dollars of equity.
This equation is the backbone of all double-entry accounting and the structure of the balance sheet. Every single transaction keeps it in balance: if the business borrows 10,000 dollars, cash (an asset) rises by 10,000 and a loan (a liability) rises by 10,000, so both sides move together. A common misconception is that equity is a pile of cash the owners can grab; it is not — it is a claim, a number, and the actual cash may be tied up in buildings, inventory, or unpaid customer bills.
A startup has 100,000 dollars in assets (40,000 cash, 60,000 equipment), owes a 60,000 dollar bank loan, leaving 40,000 dollars of equity: 100,000 = 60,000 + 40,000. If it then buys 5,000 dollars of inventory on credit, assets rise to 105,000 and liabilities to 65,000 — the equation still balances at 105,000 = 65,000 + 40,000.
Every transaction keeps Assets = Liabilities + Equity in balance.
Equity is a residual claim, not a wallet of cash. A company can show large equity yet have very little cash, because the value sits in assets like buildings, inventory, or amounts customers still owe.