Understanding your result
The principal is the mathematical amount your entered payment can amortize. It is not a lending approval or a recommended borrowing limit. Total interest is the difference between all scheduled payments and that principal.
To compare a proposed payment with gross income and other monthly debts, use the Debt-to-Income Calculator as a separate ratio check alongside your spending budget.
The formula
r is the nominal annual interest rate divided by 1,200 and n is the number of monthly payments. Each payment occurs at the end of a month. The calculation solves the present value of that payment stream without rounding each installment to cents.
A budget without interest
A payment budget of 1,000 per month over twelve months supports principal of 12,000 at zero interest. With a positive rate, part of those same payments pays interest, so the supported principal is lower.
How to use this calculator
- Decide how much your budget can allocate to loan principal and interest each month.
- Enter the quoted interest rate and repayment term in months.
- Review the implied principal and total interest together, then compare actual lender terms.
Define the payment budget carefully
For a home loan, property taxes, insurance, association charges, and maintenance can be separate from principal and interest. Subtract the costs you need to reserve before entering the loan payment budget. Otherwise the resulting principal may exceed what your broader monthly budget can support.
A longer term can support a larger loan at the same monthly payment, but commits you to more payments and can increase total interest. The calculation does not inspect your income stability, other debts, emergency savings, or future obligations. Those factors matter when deciding what payment is manageable.
Assumptions & limitations
What this calculation assumes
- The rate and monthly payment remain constant.
- The loan fully amortizes with no balloon payment.
- No fees are deducted from the principal or added to payments.
What to keep in mind
- Lender underwriting, credit checks, income multiples, and collateral restrictions are not modeled.
- Actual daily interest and rounding may change a lender quote.
Common questions
Is this the maximum a lender will approve?
No. It is an equation based on the payment you entered. A lender applies its own eligibility and affordability checks.
Should I enter a total housing budget?
Only after removing expenses that do not repay loan principal or interest. The result assumes the entire entered payment services this loan.