Official Mortgage Compare Calculator Guide

MortgageCompareCalculator.com is free, runs entirely in your browser, and requires no account. This guide walks you through your first session from start to finish: entering a loan, reading what the numbers mean, opening a second scenario, using the Compare view to find the better deal, and saving your work.

Step 1: Enter your loan details

When you open the calculator, two tabs are already ready - CALC 1 and CALC 2 - each pre-loaded with the same defaults so you can jump straight into a comparison. The starting values are:

• Country: USA
• Loan Program: Conventional
• Home Price: $800,000
• Down Payment: $160,000 (20%)
• Mortgage Type: Fixed Rate at 4.5%
• Amortization Period: 30 years
• Payment Frequency: Monthly on CALC 1, Bi-weekly Accelerated on CALC 2

Replace these with your own numbers. The Down Payment fields are linked - change the dollar amount and the percentage updates automatically, or vice versa. If you select Canada as the country, the calculator switches to CAD, applies legally required semi-annual compounding for fixed-rate mortgages, and reveals Canadian-specific fields like CMHC insurance and the mortgage term section.

For an Adjustable Rate Mortgage (ARM), select it from the Mortgage Type dropdown. An ARM Details section will appear where you can configure the initial fixed period, adjustment frequency, index rate, margin, and caps. The calculator also shows a three-scenario payment card: your projected payment at the lifetime floor, the fully indexed rate today, and the lifetime cap.

Step 2: Add the true monthly cost

A mortgage payment alone is not your full housing cost. Expand the Monthly Homeowner Expenses section to add:

• Property Taxes - defaults to 1.2% of home price annually (roughly the US national average). Switch to a fixed dollar amount if you know your actual tax bill.
• Home Insurance - defaults to $1,200/year. Enter your actual premium.
• HOA / Utilities - defaults to $0. Add any monthly HOA fees or recurring utility costs you want to factor in.

Each field can be toggled between a percentage of home price and a fixed dollar amount. Including these costs gives you the same total monthly payment figure your lender will use when qualifying you - not just the principal and interest.

Step 3: Read Key Insights

Beneath the input fields, the Key Insights section shows six summary cards that update instantly as you change any input:

• Payment Amount - your base principal + interest payment per selected payment period.
• Total Monthly Payment - your base payment plus all homeowner expenses (taxes, insurance, HOA), normalized to a monthly figure. This is the number to use for budget planning.
• Total Interest - the cumulative interest paid to the lender over the full amortization period. This is one of the most important numbers for evaluating the true cost of a loan.
• Total Cost - principal plus total interest. On a 30-year loan, total interest often exceeds the original loan amount.
• Total Extra Payments - the sum of all recurring and one-time extra payments you have entered.
• Last Payment Date - the month and year your mortgage will be fully paid off, accounting for any extra payments.

Step 4: Open the amortization schedule

Scroll down to the Amortization Schedule. Payments are grouped by calendar year; click any year to expand it and see the month-by-month breakdown of principal, interest, expenses, extra payments, and remaining balance.

For ARM and variable-rate mortgages, the schedule shows rate adjustment markers so you can see exactly when and by how much your rate changes.

You can enter a one-time extra payment on any individual row by clicking into the Extra Payments cell for that month. This is useful for modeling lump-sum payments like a tax refund or year-end bonus - the remaining balance and all Key Insights figures recalculate immediately.

Step 5: Open a second tab and set up your comparison

Click the + button next to the calculator tabs to open CALC 2 (or CALC 3 for a third scenario). Each tab is fully independent - you can set a different rate, term, down payment, or loan program in each one.

To keep things organised, double-click a tab label (or click the pencil icon that appears on hover) and rename it with something descriptive, such as "30yr Fixed 6.75%" or "15yr Fixed 6.25%". Tab names can be up to 24 characters.

To close a tab, hover over it and click the x icon. A confirmation dialog will appear before closing since all inputs in that tab will be lost. You cannot close the last remaining tab.

Step 6: Read the Compare view

Once two or more tabs are open, a COMPARE tab appears. Click it to see the full side-by-side analysis. The Compare view has seven sections:

• Winner Banner - a dark navy hero bar that immediately names the winning scenario, ranked by lowest total interest paid. It shows how much interest and how many total payments you save, plus a chip showing how many years earlier the winner pays off. Hidden entirely when all scenarios are tied.
• Scenario Header Cards - two color-coded cards side by side, one per scenario, each showing mortgage type, rate, term, and home price. The average monthly payment is the dominant number. The winning scenario receives a "Better deal ?" chip.
• Metrics Bar Grid - four key metrics (Monthly Payment, Total Interest Paid, Total Cost, Payoff Date) as comparative horizontal bar charts. Bar widths are proportional to each scenario's value so you instantly see the gap. A plain-language callout beneath each panel summarises the dollar difference.
• Mortgage Balance Over Time - an area chart showing how each scenario's outstanding balance falls over time. The gap between the two curves is visible as a filled region.
• Total Cost Breakdown - two donut charts side by side, each showing how total spend splits across principal, interest, down payment, homeowner expenses, and extra payments.
• Smart Comparison Table - a collapsible three-section table covering Mortgage Info, Payment Breakdown, and Lifetime Totals. Winner cells are highlighted in green, and key rows include inline badges so the advantage is explicit.
• Insight Strip - a dark navy footer with three plain-language takeaways: the break-even month (when the winner starts costing less), the rate difference impact (estimated cost per 1% over the full term), and which scenario builds more equity by year 5. Only shown when exactly two scenarios are active.

Step 7: Model extra payments

Extra payments go directly to principal, which reduces your balance faster and cuts the total interest you pay. There are two ways to add them:

• Recurring Extra Payments - expand the Recurring Extra Payments card and enter an amount, frequency (monthly, bi-weekly, or yearly), start date, and optional end date. Leave the end date blank to continue for the full remaining amortization. The Key Insights section updates instantly.
• One-Time Extra Payments - scroll to the amortization schedule, expand the target year, and click the Extra Payments cell for the specific month you want. Type the lump-sum amount. This is ideal for modeling a tax refund, year-end bonus, or the proceeds from selling an asset.

To see the full impact, open a second tab without the extra payment. The Compare view will show exactly how much interest you save and how many months earlier you pay off with the extra payments in place. For US conventional loans below 20% down, extra payments also bring the PMI cancellation date closer - the Compare view has dedicated PMI rows to quantify that saving.

Step 8: Save, Share, and Download

The three toolbar buttons at the top of the calculator let you preserve and export your work:

• Save - compresses all your tab inputs into a code appended to the page URL as a ?s= parameter. No data is sent to a server. Bookmark the updated URL to return to your exact scenario at any time. A "Changes not saved" banner appears whenever you modify inputs after your last save, reminding you to save again before bookmarking or sharing.
• Share - opens a dialog displaying the full URL with your current calculator state. Copy and send it to a co-borrower, financial advisor, or real estate agent. When the recipient opens the link, the calculator loads with all your tabs and inputs exactly as you left them.
• Download - instantly exports all calculations to a formatted Excel (.xlsx) file. The file includes one sheet per open tab (inputs, Key Insights, full amortization schedule) plus a Comparison sheet when two or more tabs are open. Dollar amounts are formatted as true numbers so you can continue working with them in Excel.