AtlasCalcsUtility Calculation Suite
2026-09-21 7 min read

Mortgage Amount Calculator

How much mortgage a target payment supports for a mortgage. Live calculator with worked steps, charts.

Calculator

Target Monthly Payment
$
Annual Interest Rate(%)
%
Loan Term(years)
years
Down Payment(%)
%
Property Tax Rate (annual % of value)(%)
%
Annual Homeowners Insurance
$
HOA Dues (monthly)
$

This mortgage basics calculator runs on the standard amortisation model: interest is charged on the outstanding balance each month, and anything extra you enter is applied to principal immediately.

Results

Optimal

Affordable Home Price

$383,297

With 20% down ($76,659 in cash).

Supportable Loan Amount

$306,638

Principal & Interest in Target

$2,250

Taxes & Insurance in Target

$150

Target Monthly Payment

$2,400.00/month

Total Interest Over the Term

$503,362

Down Payment Required

20.00%

Cash Needed at Closing (down only)

$76,659

Closing costs come on top of this figure.

Live results update as you type — currently showing affordable home price of $383,297 on 12 payments a year. Replace the defaults with your own quote for an exact comparison.

Visualizations

Price by Down Payment Scenario

340,70910% down
383,29720% down
438,05430% down

Where the Target Payment Goes

Principal & interest94%
Taxes0%
Insurance & HOA6%

Formula

A ratio compares an obligation with the resource that supports it. Debt-to-income compares payments with gross income, loan-to-value compares the loan with collateral, and debt-service-coverage compares net operating income with annual debt service. Each has a conventional threshold, and crossing one usually means a smaller loan, a co-borrower, or a decline.

See the worked steps below for the exact relationship used

Variables

SymbolNameUnitDescription
AAmountcurrencyBalance or amount involved in the calculation
iPeriodic ratedecimalAnnual rate ÷ periods per year
nNumber of periodscountTerm in payments

Explanation

A ratio compares an obligation with the resource that supports it. Debt-to-income compares payments with gross income, loan-to-value compares the loan with collateral, and debt-service-coverage compares net operating income with annual debt service. Each has a conventional threshold, and crossing one usually means a smaller loan, a co-borrower, or a decline.

Step-by-Step Calculation

Follow each step to understand how the result is calculated from your inputs.

Step 1

Reserve the tax and insurance share of your target payment first.

Housing budget = target − taxes − insurance
Target:$2,400.00
Taxes + insurance:$150.00
Result: $2,250.00 for principal & interest
Step 2

Discount that payment stream at the mortgage rate to find the loan it supports.

A = P × (1 − (1 + i)^−n) ÷ i
Payment:$2,250.00
Payments:360
Result: $306,638 loan
Step 3

Gross the loan up by the down payment share to get the purchase price.

Price = loan ÷ (1 − down %)
Intermediate: $306,638 ÷ 0.80
Result: $383,297
Final Answer
$383,297

Worked Examples

See how the calculator works with different scenarios.

Scenario

The mortgage amount calculator run on the values above, showing the full calculation path rather than only the answer.

Inputs

Rate:8
Years:30

Calculation

1. Reserve the tax and insurance share of your target payment first. → $2,250.00 for principal & interest 2. Discount that payment stream at the mortgage rate to find the loan it supports. → $306,638 loan 3. Gross the loan up by the down payment share to get the purchase price. → $383,297

Result

Affordable Home Price: $383,297

Interpretation

Target payment $2,400.00 supports a $306,638 loan at 8.00% over 30 years, i.e. a $383,297 purchase at 20% down.

Understanding Your Result

Your Result: Affordable Home Price: $383,297

Typical range: With 20% down, roughly $145–160 of monthly principal-and-interest capacity supports each $25,000 of loan at current 30-year rates.

What This Means

A ratio compares an obligation with the resource that supports it. Debt-to-income compares payments with gross income, loan-to-value compares the loan with collateral, and debt-service-coverage compares net operating income with annual debt service. Each has a conventional threshold, and crossing one usually means a smaller loan, a co-borrower, or a decline.

Why It Matters

Target payment $2,400.00 supports a $306,638 loan at 8.00% over 30 years, i.e. a $383,297 purchase at 20% down.

Professional Interpretation

Target payment $2,400.00 supports a $306,638 loan at 8.00% over 30 years, i.e. a $383,297 purchase at 20% down.

How this is calculated

A ratio compares an obligation with the resource that supports it. Debt-to-income compares payments with gross income, loan-to-value compares the loan with collateral, and debt-service-coverage compares net operating income with annual debt service. Each has a conventional threshold, and crossing one usually means a smaller loan, a co-borrower, or a decline.

What drives the result

A ratio compares an obligation with the resource that supports it. Debt-to-income compares payments with gross income, loan-to-value compares the loan with collateral, and debt-service-coverage compares net operating income with annual debt service. Each has a conventional threshold, and crossing one usually means a smaller loan, a co-borrower, or a decline.

Recommendations

  • •Keep a reserve after closing: lenders want 2–6 months of payments in savings, and repairs do not wait.
  • •Property tax rates vary sharply by county — use the actual millage rate for the homes you are considering.

Educational Content

Introduction

Lenders qualify borrowers on ratios, not on intuition: how much of your income is committed to debt, how much collateral backs the loan, and whether the income the asset produces covers its debt service. These calculators put the same numbers a credit officer would use in your hands before you apply.

Concept Explanation

A ratio compares an obligation with the resource that supports it. Debt-to-income compares payments with gross income, loan-to-value compares the loan with collateral, and debt-service-coverage compares net operating income with annual debt service. Each has a conventional threshold, and crossing one usually means a smaller loan, a co-borrower, or a decline.

Applications

▸Pre-qualifying yourself before a lender runs a credit check
▸Sizing a purchase so the payment fits a target ratio
▸Testing how paying off one debt changes your borrowing power
▸Stress-testing a commercial loan against a lender minimum coverage ratio

Benefits

  • •Shows the maximum amount supported by your own figures
  • •Identifies which ratio is the binding constraint
  • •Quantifies how much headroom remains before a threshold
  • •Lets you compare a stretch scenario with a comfortable one

Limitations

  • •Lenders apply overlays, compensating factors and their own credit-tier pricing
  • •Student-loan payments, leased vehicles and child support are counted differently by different programmes
  • •Self-employed income is usually assessed on tax returns rather than gross revenue
  • •A ratio that passes on paper can still fail on credit history, reserves or documentation

Best Practices

  • •Use gross income for debt ratios and net income for your own budget
  • •Pay down revolving balances rather than shuffling debt between cards
  • •Keep the requested amount at the comfortable ratio, not the maximum
  • •Re-run the numbers after any rate change — the same payment supports a smaller loan as rates rise

Common Misconceptions

Myth: A pre-approval guarantees funding
Truth: Pre-approvals are conditional on documentation, appraisal and final underwriting.
Myth: A high income always qualifies
Truth: Existing obligations, credit history and collateral matter as much as income.

Practical Tips

  • •Use gross income for debt ratios and net income for your own budget
  • •Pay down revolving balances rather than shuffling debt between cards
  • •Keep the requested amount at the comfortable ratio, not the maximum

Common Mistakes

A pre-approval guarantees funding
Pre-approvals are conditional on documentation, appraisal and final underwriting.
A high income always qualifies
Existing obligations, credit history and collateral matter as much as income.

Assumptions

This calculator makes the following assumptions to provide estimates:

Figures as entered: The result follows directly from the values you supplied.

Limitations

Be aware of these limitations when using this calculator:

Limitation: Lenders apply overlays, compensating factors and their own credit-tier pricing
Limitation: Student-loan payments, leased vehicles and child support are counted differently by different programmes
Limitation: Self-employed income is usually assessed on tax returns rather than gross revenue
Limitation: A ratio that passes on paper can still fail on credit history, reserves or documentation

Frequently Asked Questions

Answers to common questions about this calculator.

Who uses the mortgage amount calculator?
It is used by home buyers comparing mortgage offers, by owners weighing a refinance or equity move, and by loan officers and advisers sanity-checking a payment, ratio or fee structure. It sits in the Mortgage Basics group of the Mortgage & Home Finance section of Atlascalcs.
How accurate is the mortgage amount calculator?
Every figure follows directly from the inputs using standard amortisation mathematics, so it is accurate to the quality of the values you enter. Lenders round payments and apply their own day-count conventions, so expect small differences against a formal statement or payoff quote.
How current are the rates and thresholds used here?
The calculator uses the figures you enter, so update the rate to your actual offer or current market quote. Ratio thresholds, poverty guidelines and programme rules reflect the conventions described in the references and change periodically.
Does rounding change the results?
Every calculation runs on full precision and rounds only for display. Lenders round payments to the nearest cent or dollar, so expect a small difference between these figures and a formal statement or payoff quote.
Should I use the payment or the total cost to compare offers?
Use the payment to judge cash flow and the finance charge or APR to judge cost. When two offers differ on both, the all-in cost over the period you expect to hold the loan is the decisive measure.
Can I use this calculator for a business or commercial loan?
Yes. The payment, amortisation, ratio and cost calculators apply the same amortisation mathematics to commercial loans; the difference is in the fees, covenants and collateral rules, which you should enter explicitly.
What information should I have ready before applying?
Your exact rate and term, the fee schedule, any required add-ons, and your gross income and existing monthly obligations. With those five numbers every figure on this page can be tied back to a lender quote.

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Related Guides

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Glossary

Technical terms used in mortgage calculations explained in plain language.

Principal
The amount borrowed, excluding interest and fees. Payments applied to principal reduce the balance and therefore future interest.
Amortisation
Repaying a debt through a schedule of payments that gradually shifts the split from interest to principal until the balance reaches zero.
APR (Annual Percentage Rate)
The yearly cost of credit expressed as a rate, including interest and most upfront finance charges.
Finance charge
The total dollar cost of credit, including interest and certain fees.

Authoritative References

Trusted sources and standards referenced by this calculator.

Applicable Standards

Level-payment (simple-interest) amortisation, payments assumed in arrearsAPR computed by discounting the actual payment stream to net proceedsDebt ratios computed on gross income for lender comparisonsMoney rounded for display only; all calculations run at full precision

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Page Information

Last Updated:

2026-09-21

Version:

2.0.0

License:

Free to use for educational and professional purposes.