How to use the comparison mortgage comparison calculator
Prepare the values for this calculation
Compare two fixed-rate mortgage scenarios and estimate simple upfront-cost break-even time. Use the formula below to check that it answers your question. Read the input units before transferring figures from a statement, measurement or dataset.
Enter and check each input
- Loan principal: enter a value at least 0. Use the unit named in the label or selected above. Do not leave this required field blank.
- Current/option A rate (%): enter a value at least 0 and no more than 100. Use the unit named in the label or selected above. Do not leave this required field blank.
- Option B rate (%): enter a value at least 0 and no more than 100. Use the unit named in the label or selected above. Do not leave this required field blank.
- Term (years): enter a value at least 0.01 and no more than 50. Use the unit named in the label or selected above. Do not leave this required field blank.
- Switch/refinance costs: enter a value at least 0. Use the unit named in the label or selected above. Do not leave this required field blank.
- Extra payment under option B: enter a value at least 0. Use the unit named in the label or selected above. Do not leave this required field blank.
The input table gives a complete example. Keep units and time periods consistent across related fields.
Calculate and resolve any input error
Choose Calculate after entering the values. Changes also update the answer after a short pause. If an error appears, follow its message, correct the field and calculate again. Reset restores the example values.
Interpret the answer
Check Mortgage result first. With the unchanged example inputs, it is $210.41 lower required monthly payment under B. Compare the additional metrics with the primary result; each has its own label and unit.
Compare and keep a useful result
For a controlled comparison, keep every other example input unchanged and change Loan principal from 320000 to 352000. The resulting Mortgage result is $231.45 lower required monthly payment under B. This illustrates the equation’s response to that input, rather than a forecast of real events.
Read the chart’s axis labels and data table. A scenario curve changes one stated input while holding the others fixed; it does not add external observations. Use Download graph to save an available chart as a PNG.
Use Copy result or Download CSV to keep the answer. Share tool shares the page address without placing your input values in the URL. Recheck inputs and assumptions before using the result for a decision.
Comparison Mortgage Comparison Calculator formula
Each option uses the standard fixed-payment formula. Break-even months equal switching costs divided by modeled monthly savings when savings are positive.
Inputs and units
| Input | Format / range | Example |
|---|---|---|
| Loan principal | minimum 0 | 320000 |
| Current/option A rate (%) | minimum 0; maximum 100 | 7 |
| Option B rate (%) | minimum 0; maximum 100 | 6 |
| Term (years) | minimum 0.01; maximum 50 | 30 |
| Switch/refinance costs | minimum 0 | 6000 |
| Extra payment under option B | minimum 0 | 0 |
Worked example
Using the example inputs above, the mortgage result is $210.41 lower required monthly payment under B.
- Mortgage result
- $210.41 lower required monthly payment under B
- Option A required payment
- $2,128.97
- Option B required payment
- $1,918.56
- Option B extra principal per month
- $0.00
- Option B modeled cash payment
- $1,918.56
- Option A scheduled interest
- $446,428.47
- Option B modeled interest
- $370,682.20
Results and assumptions
Break-even uses required-payment savings only; voluntary extra principal is shown separately. Comparison excludes taxes, insurance, opportunity cost and lender-specific terms unless entered as switching costs.
Fix an input or unexpected result
Loan principal is required. Enter loan principal using the format and bounds in the input table. Zero and an empty field are different: use zero only if it is allowed and represents your data.
If your answer differs from the example, choose Reset and compare every field, including selected units and options. Check percentage versus decimal entry and whether values describe the same period. Round only the final displayed answer when reproducing the formula.
If a discrepancy remains, report the calculator issue with the page address, non-sensitive example inputs, actual result, expected result and a reference for your calculation.