The Accounting Equation

Assets are everything of value a business owns or controls — cash, equipment, inventory, buildings, and money owed to it by others.

Liabilities are everything the business owes to outsiders — bank loans, unpaid bills, money borrowed in any form.

Equityis what's left over for the owners once liabilities are subtracted from assets — the owners' own claim on the business.

The accounting equationties the three together: Assets = Liabilities + Equity. This isn't a target a business aims for — it's true by definition, for any business, at any moment, no matter what happens.

A business can't just have things appear out of nowhere — every dollar of value it holds, whether in cash, equipment, or anything else, had to come from somewhere. There are only two possible sources. Someone lent it to the business — a bank loan, an unpaid bill owed to a supplier, money borrowed in some form — which creates an obligation to eventually pay it back. Or the owners supplied it themselves, either by putting money in directly or by leaving past profits inside the business instead of taking them out — which creates the owners' own claim on the business.

Because those are the only two possible sources of anything a business owns, adding up everything owed to outside lenders and everything that belongs to the owners has to exactly equal everything the business owns. This isn't a rule accountants chose to enforce — it's just a restatement of the fact that every asset was paid for by either debt or ownership, with no third option. Assets = Liabilities + Equity holds because there is nowhere else asset value could have come from.

This is why the accounting equation is usually treated as the foundation of accounting: every transaction a business records changes at least two of these three categories at once, in a way that keeps the equation balanced. That's also the root idea behind double-entry bookkeeping — recording every transaction on (at least) two sides so the equation never falls out of balance, which in turn is what makes it possible to catch recording errors.

The identity, and an equivalent way to rearrange it:

Assets = Liabilities + Equity
Equity = Assets − Liabilities

• Assets — everything of value the business owns or controls
• Liabilities — everything the business owes to others
• Equity — what remains for the owners once liabilities are subtracted from assets

The second form is useful on its own: it's how you find out what a business is really worth to its owners once every obligation is accounted for.

Maria starts a small bakery. She puts in $10,000 of her own savings and takes out a $5,000 loan from a bank to buy an oven and initial ingredients.

Assets (cash + oven + ingredients): $15,000   ($10,000 + $5,000 borrowed)
Liabilities (owed to the bank):      $5,000
Equity (Maria's own stake):          $10,000

Check: $15,000 = $5,000 + $10,000 ✓

Now suppose the bakery spends $2,000 cash on flour and sugar (inventory). Total assets are unchanged — $2,000 of cash simply became $2,000 of inventory — so the equation still holds at $15,000 total assets, with liabilities and equity untouched. The equation balances because this transaction only moved value between two assets; it didn't create or use up any borrowed or owner money.