A lender quoted you a monthly payment. Or you're running numbers before you even talk to one. These guides break down how mortgage and loan payments are calculated — the principal, the interest, what your down payment really changes — so you can verify any number before you commit to it. No email. No one trying to pre-qualify you.
← All GuidesRefinancing saves money only if you stay past the break-even. Learn the formula, what closing costs include, and how to run the numbers before you commit.
Read guide →Your DTI ratio is the number lenders check before your credit score. Learn how to calculate it, what thresholds matter, and how to lower it fast.
Read guide →See how each mortgage payment splits between principal and interest — and why only $246 of a $1,996 payment reduces your balance on a $300K loan.
Read guide →Learn the exact formula every lender uses to calculate monthly payments, with step-by-step examples for any loan amount, rate, and term.
Read guide →The exact formula behind every car payment, how interest front-loads against you, and the numbers every car buyer needs before signing.
Read guide →See exactly how long your credit card debt will take to pay off and what it'll cost in interest — with a step-by-step formula and free payoff calculator.
Read guide →Learn the 28/36 rule, the DTI formula banks actually use, and how income, debt, down payment, and credit score interact to determine your maximum home purchase price.
Read guide →Learn the exact PMT formula lenders use to calculate your monthly mortgage payment, with step-by-step examples, amortization breakdowns, and a full comparison table.
Read guide →