Mortgage Rate Calculator for Comparing Interest Rate Deals
Compare monthly principal-and-interest payments at three mortgage rates on the same home price, down payment, and term.
Enter home price, down payment, term, and three interest rates to see each monthly payment and which quote produces the lowest draft.
Mortgage Rate Calculator for Comparing Interest Rate Deals
Compare monthly principal-and-interest payments at three mortgage rates on the same home price, down payment, and term.
About the Mortgage Rate Calculator
The mortgage rate calculator isolates the effect of the note rate on monthly principal and interest. Shoppers use it when three lenders, or three lock options from one lender, quote different rates on the same purchase. Enter home price, down payment, term in years, and three annual interest rates. Principal is price minus down payment. Closing costs are collected as a reminder of cash to close; they do not change the payment ranking because they are not amortized in this form.
Each payment uses the standard fixed-rate formula with monthly rate i = r/12 and n = years × 12. The headline result is the lowest of the three payments. That makes it easy to see how much a quarter-point or half-point really moves the draft before you mix in points, credits, or different loan amounts. Taxes, insurance, PMI, and HOA are omitted on purpose so a rate difference is not confused with an escrow difference.
Use the mortgage rate calculator when a 30-year quote sits next to a 15-year quote only after you put both on the same term field, when a buydown is advertised against a par rate, and when you want a clean P&I comparison to take into a lock conversation. If one quote requires buying points, run the mortgage points calculator as well; a lower rate that costs thousands at closing can still lose on a short holding period.
Ask each lender whether the quoted rate assumes points, a float-down, or a credit that raises the rate, because those terms will not appear in the three payment lines. Rate locks expire, underwriting can change the price after credit or appraisal, and discount points can reprice overnight. Recalculate when any of the three quotes change, and keep home price and down payment identical across the comparison. The result is a planning estimate of principal and interest, not an APR, not a Loan Estimate, and not a total-cost ranking that includes fees.
Mortgage Rate Calculator Examples
These worked examples use the same amortization payments as the mortgage rate calculator.
| Inputs | Result | Why it matters |
|---|---|---|
| $400,000 price, $80,000 down, 30 years, rates 6.5% / 6.0% / 5.5% | Payments $2,022.62 / $1,918.56 / $1,816.92; lowest $1,816.92 | Each half-point drop saves about $100–$105 per month on this $320,000 principal. |
| $350,000 price, $70,000 down, 15 years, rates 6.25% / 5.875% / 5.5% | Payments $2,400.78 / $2,343.93 / $2,287.83; lowest $2,287.83 | On a 15-year term the same rate gaps move the payment by smaller dollar amounts. |
| $800,000 price, $160,000 down, 30 years, rates 7.0% / 6.5% / 6.25% | Payments $4,257.94 / $4,045.24 / $3,940.59; lowest $3,940.59 | A jumbo principal magnifies a quarter-point difference into more than $100 a month. |
How to Use the Mortgage Rate Calculator
- Enter the home price, down payment, and loan term so all three quotes share the same principal.
- Enter the three annual interest rates you are comparing.
- Select Calculate to view each principal-and-interest payment and the lowest payment.
- If a lower rate requires points, compare those costs separately before treating the lowest payment as the best deal.
Mortgage Rate Calculator FAQ
Are taxes and insurance included?
No. The comparison is principal and interest only so the rate effect is easy to see. Add escrow items after you pick a rate if you need a full PITI budget.
Do closing costs change the ranking?
Not in this calculator. Closing costs are a cash-to-close reminder and are not added to the payments. Two rates can rank differently once points and credits are included.
Is the lowest payment the cheapest loan?
It is the cheapest monthly P&I among the three rates on this principal and term. Origination fees, points, and a shorter expected holding period can still favor a higher rate.
Can I compare a 15-year rate with a 30-year rate?
Only if you put the same term in the term field for the whole form. To compare different terms, use the mortgage comparison calculator instead.
How is principal calculated?
Principal is home price minus down payment. Entering an already-netted loan amount plus a down payment would shrink the loan twice and understate every payment.