Home Loan Comparison Calculator: Compare Payments

A home loan comparison tool estimates and compares the principal-and-interest payments and total interest for two home loans using their loan amounts, APRs, and terms. Enter the figures offered by a lender to see the payment difference; the result does not determine approval or include the full cost of owning a home.

Formula

This comparison uses the standard fixed-rate, fully amortizing loan payment formula. For each loan, monthly payment is M = P × r ÷ [1 − (1 + r)⁻ⁿ], where P is the amount borrowed in dollars, r is the monthly interest rate as a decimal, and n is the number of monthly payments. Convert an APR quoted as a percentage per year using r = APR ÷ 1,200; convert the term in years using n = years × 12.

The first result is Loan A’s payment minus Loan B’s payment. A positive result means A’s calculated monthly principal-and-interest payment is higher; a negative result means B’s is higher. Total interest for each loan is estimated as M × n − P, and the final result subtracts B’s total from A’s. The displayed calculations use unrounded formula values before showing two decimal places, so a manually recomputed total using payments rounded to cents may differ slightly.

Worked Example

Using the defaults for both loans: each amount is $300,000, each APR is 6.5%, and each term is 30 years.

• Monthly rate: 6.5 ÷ 1,200 = 0.0054167.
• Number of payments: 30 × 12 = 360.
• Loan A payment: $300,000 × 0.0054167 ÷ [1 − (1 + 0.0054167)⁻³⁶⁰] = $1,896.20 per month, rounded to cents.
• Loan B has the same inputs, so its payment is also $1,896.20 per month.
• Payment difference: $1,896.20 − $1,896.20 = $0.00 per month.
• Using the unrounded payment in the formula, each loan’s total interest is approximately $382,632.14; the interest difference is $0.00.

The payment and interest figures are principal-and-interest estimates, not a quoted bill or payoff statement.

Assumptions

• Each loan has a fixed APR and level monthly payments for the full stated term.
• Payments are assumed to occur monthly; the calculation uses monthly interest at APR divided by 12.
• The model assumes a fully amortizing loan with no extra payments, missed payments, or changes in rate.
• Fees, taxes, homeowners insurance, mortgage insurance, escrow, and other housing costs are not included.

How to Compare Home Loan Offers

Use figures that describe the same transaction and check the details behind each quote. The amount borrowed should match the expected principal, not the home’s purchase price if a down payment is involved. Enter the loan’s stated APR and repayment term, and confirm whether the offer is fixed-rate or adjustable. This calculator models only a fixed rate, so it cannot represent future payment changes on an adjustable-rate loan.

For a useful comparison, gather the following from each lender’s written estimate or disclosure:

• Principal amount and whether any costs are added to the balance.
• APR and note rate, since they are not necessarily interchangeable; use the APR here as a simplified annual rate input, and verify how the lender defines the quoted figures.
• Repayment length and whether payments begin immediately or follow a different schedule.
• Upfront charges, recurring charges, and any rate discount tied to points or other costs.
• Whether the rate is fixed, and, if not, how and when it can change.

The tool isolates payment arithmetic. It cannot determine which offer has lower total cost when offers have different fees, points, insurance requirements, or payment structures. Compare those items separately using the lender’s documents. Rates and fees are lender-specific inputs; obtain the applicable figures directly from the lender rather than relying on an example.

Reading the Results and Common Pitfalls

A monthly payment is only one dimension of a loan. A longer term often produces a lower scheduled monthly principal-and-interest payment for the same principal and APR, while the loan remains outstanding for more months. That can result in greater total interest over the full schedule. A shorter term can have higher monthly payments but fewer scheduled payments. The calculator’s interest comparison makes this trade-off visible under its assumptions; it does not account for the time value of money or other costs.

A $0.00 difference means the entered inputs produce equal results at the displayed precision, not that the offers are identical. Differences in fees, rate adjustment provisions, payment timing, or included costs can matter even when the displayed payments match. Check the full disclosures and confirm that each input is on the same basis.

• Do not enter a percentage as a decimal: enter 6.5 for 6.5%, not 0.065.
• Do not compare different principal amounts unless that difference is intentional; the amount borrowed strongly affects the payment.
• Do not treat monthly principal and interest as the complete housing payment. Taxes, insurance, mortgage insurance, association charges, and maintenance may be separate.
• Do not infer that the calculated amount is an offer, approval, or guaranteed payment. Lender calculations may include details this model omits.

Limits and Alternatives

This tool is suited to a basic side-by-side comparison of fixed-rate, level-payment loans. It does not calculate closing costs, an annual percentage rate inclusive of specific fees, adjustable-rate changes, interest-only periods, balloon payments, or the effect of extra principal payments. It also does not assess eligibility, affordability, taxes, legal obligations, or lender practices.

For a fuller comparison, request written loan estimates and review both the cash needed at closing and the scheduled payments over time. A separate amortization schedule can show how each payment is divided between interest and principal. If an offer includes fees, points, temporary rate reductions, or a variable rate, ask the lender to explain the payment schedule and total charges in writing. The result is an estimate; the lender’s disclosure gives the exact figures.

Frequently Asked Questions

What does a home loan comparison tool calculate?
It estimates fixed monthly principal-and-interest payments and total interest from each loan’s principal, APR, and term, then shows the difference between the two.

Should I compare APR or interest rate?
This calculator accepts an APR as a simplified annual-rate input. APR and the note interest rate can reflect different things, so check the lender’s definitions and compare written disclosures rather than assuming the figures are interchangeable.

Does the result include property taxes and insurance?
No. Taxes, homeowners insurance, mortgage insurance, escrow, fees, and other housing costs are excluded unless separately entered into another calculation.

Can I use this for an adjustable-rate mortgage?
Not for its future payment changes. The calculation assumes the rate stays fixed for the entire loan term; an adjustable-rate offer needs its adjustment schedule and applicable terms reviewed separately.

Why can a longer term lower the monthly payment but increase interest?
Repayment is spread across more months, which can reduce the scheduled payment. Interest accrues over a longer period, so total interest may be higher under otherwise matching assumptions.

Related

• Online Installment Loan Comparison Calculator
• Non-Installment Loan Calculator and Explanation
• Online Installment Loan Payment Calculator

in p1 | Loan A amount | $ | 300000 | 1 | 100000000
in apr1 | Loan A APR | % | 6.5 | 0.01 | 100
in yrs1 | Loan A term | years | 30 | 0.0833 | 50
in p2 | Loan B amount | $ | 300000 | 1 | 100000000
in apr2 | Loan B APR | % | 6.5 | 0.01 | 100
in yrs2 | Loan B term | years | 30 | 0.0833 | 50
out diff | Difference in monthly payments (A minus B) | $ | (p1 * (apr1 / 1200) / (1 - (1 + apr1 / 1200) ^ -(yrs1 * 12))) - (p2 * (apr2 / 1200) / (1 - (1 + apr2 / 1200) ^ -(yrs2 * 12))) | 2
out pmt1 | Loan A monthly principal-and-interest payment | $ | p1 * (apr1 / 1200) / (1 - (1 + apr1 / 1200) ^ -(yrs1 * 12)) | 2
out pmt2 | Loan B monthly principal-and-interest payment | $ | p2 * (apr2 / 1200) / (1 - (1 + apr2 / 1200) ^ -(yrs2 * 12)) | 2
out intdiff | Difference in total interest (A minus B) | $ | (pmt1 * yrs1 * 12 - p1) - (pmt2 * yrs2 * 12 - p2) | 2