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Loan Affordability Calculator With Up to 8 Midterm Modifications

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Loan Affordability Calculator Sign
Loan Affordability Calculator

This calculator will calculate the size of the loan you can take out based on the size of the periodic payment you can afford to make. Simply enter the rate, number of payments, and payment amount you can afford, and the calculator will tell you the size of the loan (principal). Plus, if you are a private lender, the calculator also provides for up to 8 midterm rate and/or payment modifications to help you tailor the loan to your customer's current and future financial situation. Also includes a printer friendly amortization schedule.

Learn More

Selected Data Record:

A Data Record is a set of calculator entries that are stored in your web browser's Local Storage. If a Data Record is currently selected in the "Data" tab, this line will list the name you gave to that data record. If no data record is selected, or you have no entries stored for this calculator, the line will display "None".

DataData recordData recordSelected data record: None
Date of first payment:

Date of first payment:

Select the month and day and enter the 4-digit year of date of your first payment.

Interval:Pmt interval:Payment interval:Payment interval:

Payment interval:

Select the payment interval stated in the original loan terms.

Balance:Principal amt:Principal or current payoff:Principal or current payoff amount:

Principal or current payoff amount:

If known, enter the principal balance or current payoff amount. Otherwise leave blank and complete the other three fields.

Interest rate:Interest rate:Interest rate:Annual interest rate:

Annual interest rate:

If known, enter the interest rate expressed as a percentage, but without the percent sign (for 6.5%, enter 6.5).

If the interest rate is not known, to save the calculator from making unnecessary iterations, please select your best guess from the drop down menu (default guess is 10%) and the calculator will attempt to calculate the rate for you given the other three loan terms.

# pmts:# pmts left:Number of payments left:Number of payments remaining:

Number of payments remaining:

If known, enter the number of payments remaining on the loan. Otherwise, leave blank and complete the other three fields.

Pmt:Payment amt:Monthly payment amount:Monthly payment amount:

Monthly payment amount:

If known, enter the monthly payment amount, without the dollar sign or any commas. Otherwise, leave blank and complete the other three fields.

Missing term:

Missing loan term:

This row will state the the title of the missing term that has been calculated, with the amount of the missing term located in the right-hand column.

Total years:Total years:Total years remaining:Total years remaining:

Total years remaining:

This result is the number of monthly payments remaining converted into the number of years remaining.

Total P&I:P&I:Total principal & interest:Total principal and interest payments:

Total principal and interest payments:

This result is the total of all payments between now and when the loan is paid off.

Total interest:Total interest:Total interest remaining:Total interest remaining:

Total interest remaining:

This result is the total interest that will be paid between now and when the loan is paid off.

If you would like to save the current entries to the secure database, tap or click on the Data tab, select "New Data Record", give the data record a name, then tap or click the Save button. To save changes to previously saved entries, simply tap the Save button. Please select and "Clear" any data records you no longer need.

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About the Loan Affordability Calculator

I created this online Loan Affordability Calculator in response to a request submitted by the owner of a small car dealership -- one that still does their own financing -- and who used to use a DOS program published by Andrew Tobias, called "Managing Your Money" (MYM, software that I still use to this day, but it only works on my old Mac iBook).

Unfortunately the car dealership upgraded their computer operating system and can no longer use MYM.

With his permission, here is an excerpt from the email I received from Patrick Walsh of Atwater Ford:

It would be wonderful if there was a dedicated loan calculator that someone could put in the beginning principal amount, the APR, the payment amount, and then have it compute the # of months.

Then step the payments (as in $200/mo for 12 months, followed by $235/mo for 12 months, followed by $260 for 24 months, and finally $275/month for the final 12 months).

Or with the "baby" balloons, as in $200/mo for 60 months, with a baby balloon of $500 each june and each December.

OR one with $850 each September (one per year as opposed to two per year in the first example).

MYM's loan amortization would ask you to fill in 3 out of the 4 blanks (APR, rate, # of Payments, and payment $ amount) and it would compute the one that was left open.

MYM was a brilliant piece of software that was well ahead of its time. Unfortunately, according to the author, the software hasn't been sold at retail for years and his contract for it ended years before that.

But since I still use MYM (Macintosh version #7), I was able to create a web version of the "Loan Analysis" feature of the software that Patrick no longer has access to. I have actually used this MYM feature to help answer countless loan-related questions from site visitors over the years.

Suggested Uses for the Calculator

Here are a few of the many possible uses for the Loan Affordability Calculator.

How Much Can I Afford to Borrow?

To see how much loan you can afford based on the amount of the installment payments you can afford to make, enter the interest rate, the number of payments, and the payment amount you can afford. The calculator will then tell you the size of the loan (principal) those terms will equate to.

Step or Graduated Payments and "Baby" Balloons

This use of the calculator is the one that prompted Patrick to request the calculator. He can now use this calculator to help his small-town customers to purchase the reliable transportation they couldn't otherwise afford.

Patrick can now enter the principal, rate, and affordable payment amount to calculate the initial number of payments to pay off the loan. He can then use the customer's anticipated raises and lump sum receipts (tax refunds, seasonal income, etc.) to create a graduated payment plan -- with or without "baby" balloons.

Variable Rate Loans

If you are paying on an adjustable rate loan, you can enter the original terms and then enter up to 8 rate changes that have occurred in order to get an idea of what your current payoff amount is.

Early Loan Payoff

If you want to see how much time and interest you will save by increasing the payment amount, or prepaying a lump sum of principal, the calculator will give a side-by-side comparison of the original terms versus the modified terms.

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How to use the Loan Affordability Calculator

Step #1:

Select the month and day, and enter the 4-digit year of the date of the first payment.

Step #2:

Select the loan's payment frequency.

Step #3:

Enter the three known loan terms and leave the unknown term blank.

Step #4:

Press the "Calculate Unknown" button. This will replace the "Missing term" text with the description of the calculated term, along with its numerical value.

Step #5:

If you would like to make any payment or rate modifications to the loan, tap the "Modify Loan" button. This will display a loan modification section where you can make up to 8 changes to the rate and/or payment amount.

Step #6:

To make a modification, tap the "Mod #" button for the next available modification. This will open a dialog containing where you can complete the following:

After ___ payments, change the rate to ___% and/or increase the payment by $____. Keep for [this payment] or [every payment].

Step #7

Once you have entered all modifications, swipe to the bottom of the modification panel and tap the "Recalculate" button. This will recalculate the loan based on your modifications.

Step #8

To print the amortization schedule (revised or otherwise), tap the "Amortization Schedule" button. This will open new window containing the schedule.

Saving Entries:

If your web browser supports Local Storage, you can save your entries to your web browser so won't have to start over on your next visit. Please note that your saved entries can only be retrieved from the same device and web browser you were using when you stored them. If you would like to access your saved entries from any device I invite you to subscribe to the Ad-Free Member Version.

To save your entries to your web browser, click or tap the Data tab in the Help and Tools section (mobile: top right of the main screen), select "New Data Record" from the drop-down menu, enter a name for the data record, and then tap or click the Save button.

To load previously saved entries, click or tap the Data tab and select the saved data record from the drop-down menu. You can then save any changes to your entries by simply clicking the Save button while the data record is selected.

To clear a named set of saved entries, click or tap the Data tab, select the saved data record from the drop-down menu, and then tap or click the Clear button.

Numbers and Decimals:

Only numeric characters (0-9 and decimal points) may be entered in numeric fields. Non-numeric characters (dollar signs, percent signs, commas, etc.) may cause calculation errors. If the field includes a grid icon, tapping the icon will open a popup keypad which will include only the characters allowed in the field. If your device keypad does not include a decimal point, use this popup keypad to enter decimal numbers where applicable.

Popup Tool Tips:

Tap the info (i) icons for a further explanation of each entry field (you can click [X] or outside of the pop-up tool tips to close them). A summary of these explanations, along with any additional term explanations, can also be found under the Terms tab.


Since I can't test for every possible combination of numbers, please be sure to double-check the results of this calculator yourself before considering them to be valid. If you do discover an issue with the calculated results, please report the issue using the feedback form located below the calculator.

Scrolling & Shrinking:

In order to scroll the calculator vertically you will need to swipe just outside of the calculator's dark-blue border, or use the window's far right-hand scroll bar, whichever is applicable to your device.

If the top section of the calculator becomes to tall for your viewport, tapping in the "Enter a problem..." field should reset the top section to its original height.


The Algebra Calculator is the only calculator on the site that I did not create myself. And since I did not create it, I don't have access to the code for fixing any issues you may be experiencing. So if you are having issues with the calculator, please visit the support page at for assistance.


Fields, Terms, and Definitions.

Reset button:

Clicking the "Reset" button will restore the calculator to its default settings.

Pocket Calculator

Calculate any amounts needed to enter into calculator.


Data Management

Save and retrieve entries and notes (requires HTML5 compliant web browser).

Calculator Data

Calculator Data:

If you are using the latest version of your web browser software, this feature will allow you to save your calculator entries to your web browser's local storage in between visits. This means the calculator entries can only be recalled with the same device and web browser you were using when you saved them. If you'd like to save data between devices you will need to subscribe to the Ad-Free Member Version.

Save: To save a new set of calculator entries, select "New Data Record" from the dropdown list, enter a nickname for the data record, then click the "Save" button.

Load: To load a previously saved set of calculator entries, simply select the name of the data record from the dropdown list.

Save Changes: To save changes to a set of previously saved calculator entries, be sure the name of the data record is selected, and then click the "Save" button.

Clear: To clear a saved set of entries, be sure the name of the data record is selected, and then click the "Clear" button.

Backup Data
My Notes:
Subscribe to the Cloud level of the Ad-Free Member Version to save your entries and notes to a secure online database, allowing you to access your saved entries from any device or web browser.

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Help and Tools

Help and Tools:

This section, which you can Unstick or Hide in the Calculator Preferences (just above the top of the calculator), contains the following tabs (content too long to fit within bordered frame can be scrolled up and down):

About: Click this tab for an introduction to the calculator.

Instructions: Click this tab for step-by-step instructions for using the calculator.

Terms: Click this tab for a list of the descriptions that are located within each popup help button (info icons).

PCalc: Click this tab for a handy "pocket" calculator you can use when you need to calculate an entry needed for the calculator.

Data: Click this tab to save a set of entries or a note in between visits. Entries and notes will be stored to your web browser's local storage (if supported by your browser of choice), meaning they can only be recalled with the same device and web browser you were using when you saved them. If you'd like to save entries and notes between devices you can do so by subscribing to the Ad-Free Member Version.



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