SmartHelping / Personal Finance / Excel & Google Sheets
Mortgage Savings Calculator
See how extra principal payments change your mortgage repayment schedule. Compare your original loan with a custom extra-payment plan to estimate total interest saved and the number of payments eliminated.
Immediate download after purchase. By purchasing, you agree to the Terms of Service.
Video walkthrough & spreadsheet preview
See the extra-payment simulation in action.
Core loan assumptions
Start with your mortgage terms.
Mortgage amount and interest rate
Enter the loan amount and interest rate used to calculate the repayment schedule.
Payment frequency and loan term
Set the number of payments per year, loan start date, and total loan length.
Two amortization schedules
Compare the original schedule with your extra-payment plan.
Base-case amortization
The first schedule calculates the mortgage repayment path without extra principal payments.
Extra-payment amortization
The second schedule includes a column for the extra principal payment in each period. Enter your planned amounts and the schedule updates accordingly.
Flexible period-by-period inputs
Enter extra payments that fit your budget.
An extra payment each year
Enter additional principal in selected annual periods to test a once-a-year repayment plan.
Extra principal every period
Enter an extra principal amount each payment period to compare a recurring repayment plan.
Vary the amount over time
Use different extra principal amounts in different periods rather than committing to one constant amount.
Combine payment patterns
Mix recurring extras with larger payments in selected periods and review the resulting schedule.
Savings outputs
Measure the difference in interest and repayment time.
Total interest saved
Compare the interest over the life of the mortgage under the original schedule and the extra-payment schedule.
Number of payments saved
See how many scheduled payments the extra principal plan removes from the modeled repayment period.
Comparison analysis
Review the original and extra-payment results together to understand the effect of the plan.
Dynamic visualization
Use the included visualization to see how the results change when you adjust the extra payments.
Choose your spreadsheet format
Both spreadsheet versions are included.
Excel version
Use the Excel calculator to enter mortgage assumptions and build your extra-payment schedule.
Google Sheets version
Use the Google Sheets version for the same mortgage repayment comparison. Both versions are available after purchase.
Getting started
Move from loan terms to a repayment comparison.
Enter the mortgage terms
Set the amount, interest rate, payments per year, start date, and total loan length.
Review the base schedule
Check the original amortization schedule before adding extra principal payments.
Build the extra-payment plan
Enter your expected extra principal in the relevant periods on the second schedule.
Compare the savings
Review total interest saved, payments saved, and the visualization. Adjust the extra payments to compare another plan.
Additional resources
Explore additional budgeting and financing tools.
Questions before you start
A few useful details.
What loan details do I enter?
Enter the mortgage amount, interest rate, number of payments per year, start date, and total loan length.
Can the extra principal amount change each period?
Yes. The second amortization schedule includes an extra-principal column where you can enter a different amount for each period.
Can I test one extra payment each year?
Yes. Enter additional principal in the relevant periods to model an annual extra-payment strategy.
Can I test extra principal with every payment?
Yes. Enter an extra amount in each payment period to model a recurring plan.
What does the comparison show?
It shows total interest saved over the life of the mortgage and the number of payments saved, supported by a dynamic visualization.
How many amortization schedules are included?
Two: a base case without extra payments and a second schedule with period-by-period extra principal inputs.
Are both Excel and Google Sheets included?
Yes. Both versions are available after the $45 one-time purchase.
How is the calculator delivered?
The template is immediately available to download after purchase, with access to both spreadsheet versions.
Mortgage repayment planning
See what extra principal payments could save.
Mortgage Savings Calculator — $45, Excel and Google Sheets versions included.
