The Universal Calculation Engine
Insights
The Universal Calculation Engine

How lenders decide how much you can borrow

Part of: How Much House Can You Afford?

You will see affordability on receipts, loan estimates, pay stubs, and card statements—always next to a specific dollar line.

On the statement

How Much House Can You Afford? covers the concepts. On your own paper, pick one row: a subtotal, a box on a disclosure, a line on a pay stub. Ask which dollar amount that affordability is calculated from on that row only.

Read the line

Tax, fees, and promos often reuse one % sign for different underlying amounts. This lesson and this one show two common layouts so you do not assume your card works like your mortgage form.

One real line

Pick a line on a bill that confused you. Write next to it: “percent of ___.” If the blank is empty, you and the issuer may be using different dollar amounts—not different arithmetic.

Check the math

Core lesson

Go deeper: How Much House Can You Afford?. Use the calculators below with your own loan or bill numbers, not only the examples on this page.

Use the calculator

FAQ

Where is the main lesson?

How Much House Can You Afford? pulls the topic together in one place, with links to related lessons.

Which calculator should I open first?

Use the first tool in the list for most questions. If you are reconciling payment rows on a schedule, pick amortization when it appears in the list.