Quick answer
A common rule limits housing costs to 28% of gross income and total debt to 36% (the 28/36 rule). On $90,000 a year the housing limit is $2,100 a month; with $500 of other debts the back-end limit is $2,200, so $2,100 applies. With $40,000 down at 6.5% over 30 years that supports a home of about $310,781 and a loan of $270,781.
This house affordability calculator takes income, other monthly debts, down payment, rate, term and the two ratio limits. The calculator returns the estimated maximum home price, loan amount and monthly payment.
Related tools: Down Payment Calculator: Down payment amount and loan size from a percentage. Refinance Calculator: Monthly savings and break-even time from refinancing. APR Calculator: Annual percentage rate of a loan once upfront fees are counted.
How to use the House Affordability Calculator
- Enter annual gross income ($) (above 0).
- Enter other monthly debt payments ($) (0 or more). It starts at 0.
- Enter down payment ($) (0 or more).
- Enter mortgage rate (%) (between 0 and 100).
- Enter term (years) (between 0 and 50). It starts at 30.
- Enter housing payment limit (of gross income) (%) (between 0 and 100). It starts at 28.
- Enter total debt limit (of gross income) (%) (between 0 and 100). It starts at 36.
- Enter property tax + insurance (of price, per year) (%) (between 0 and 20).
- Press Calculate to see the result, and use Reset to start again.
| Input | What to enter | Allowed values |
|---|---|---|
| Annual gross income | A number, in $ | > 0 |
| Other monthly debt payments | A number, in $ | ≥ 0, starts at 0 |
| Down payment | A number, in $ | ≥ 0 |
| Mortgage rate | A number, in % | ≥ 0, ≤ 100 |
| Term | A number, in years | > 0, ≤ 50, starts at 30 |
| Housing payment limit (of gross income) | A number, in % | > 0, ≤ 100, starts at 28 |
| Total debt limit (of gross income) | A number, in % | > 0, ≤ 100, starts at 36 |
| Property tax + insurance (of price, per year) | A number, in % | ≥ 0, ≤ 20 |
Formula and method
Formula
PITI limit = min(front × income ÷ 12, back × income ÷ 12 − other debts); price solves payment(price − down) + price × tax ÷ 12 = limit
IEEE-754 double precision; money shown to cents, rates to 4 decimals. Results are estimates, not financial advice.
28% and 36% are common guidelines and are editable; lenders set their own limits.
Worked examples
These examples are verified: each one is an automated test case that the live calculator must reproduce exactly.
Example 1
Inputs: Annual gross income = 90000; Other monthly debt payments = 500; Down payment = 40000; Mortgage rate = 6.5; Term = 30; Housing payment limit (of gross income) = 28; Total debt limit (of gross income) = 36; Property tax + insurance (of price, per year) = 1.5.
| Result | Value |
|---|---|
| Estimated maximum home price | $310,781.48 |
| Loan amount | $270,781.48 |
| Maximum monthly payment | $2,100.00 |
Example 2
Inputs: Annual gross income = 120000; Other monthly debt payments = 0; Down payment = 60000; Mortgage rate = 6; Term = 30; Housing payment limit (of gross income) = 28; Total debt limit (of gross income) = 36; Property tax + insurance (of price, per year) = 1.2.
| Result | Value |
|---|---|
| Estimated maximum home price | $451,680.07 |
| Loan amount | $391,680.07 |
| Maximum monthly payment | $2,800.00 |
The first line is the headline result (estimated maximum home price). Below it the house Affordability Calculator lists loan amount and maximum monthly payment, which describe the same case from other angles. IEEE-754 double precision; money shown to cents, rates to 4 decimals. Results are estimates, not financial advice.
Front-end and back-end ratios
The front-end ratio is housing costs (mortgage, property tax, insurance) divided by gross income: 28% of $7,500 a month is $2,100. The back-end ratio adds other debts such as car loans and cards: 36% of $7,500 is $2,700, less $500 of debts leaves $2,200. The lower of the two limits sets the budget.
Reading the result
Of the $2,100, about $1,712 pays principal and interest on the $270,781 loan and the remaining $389 covers property tax and insurance at the rate entered. Mortgage insurance and HOA fees are excluded, and lenders apply their own limits, so a lender's approval can differ. FHA and VA loans allow higher ratios; the limits here are editable.
How the result changes with annual gross income
Holding every other input at the first worked example, this table changes only annual gross income. It shows how sensitive the answer is to that one value; each row was produced by running this calculator.
| Annual gross income | Estimated maximum home price | Loan amount | Maximum monthly payment |
|---|---|---|---|
| 45000 | $145,670.82 | $105,670.82 | $850.00 |
| 90000 | $310,781.48 | $270,781.48 | $2,100.00 |
| 180000 | $588,167.39 | $548,167.39 | $4,200.00 |
| 360000 | $1,142,939.20 | $1,102,939.20 | $8,400.00 |
What happens with invalid input
These messages are produced by the calculator itself, so you know what to fix.
- Other monthly debt payments: entering "5000" shows "Your other debts already use the whole payment budget." beside that field and no result.
- Annual gross income: entering "0" shows "Annual gross income must be greater than 0." beside that field and no result.
Choosing between the House Affordability Calculator and similar calculators
Each row shows what a related calculator on this site asks for and what it returns, so you can pick the one that matches your question.
| Calculator | You enter | It returns |
|---|---|---|
| [Down Payment Calculator](/real-estate/down-payment-calculator/) | home price and down payment | Down payment |
| [Refinance Calculator](/finance/refinance-calculator/) | current balance, current rate and current remaining term | Monthly savings |
| [APR Calculator](/finance/apr-calculator/) | loan amount, upfront fees and note rate | APR |
| [Amortization Calculator](/finance/amortization-calculator/) | loan amount, interest rate and term | Monthly payment |
| [Mortgage Calculator](/real-estate/mortgage-calculator/) | home price, down payment and interest rate | Total monthly payment |
Background: loans and mortgages
The interest rate is the cost of borrowing the principal; the APR also folds in certain fees, so a lower rate with high fees can have a worse APR. These calculators use the rate you enter and do not add fees, insurance or taxes, so add fees to the principal if you want to include them.
A fixed-rate loan is paid in equal instalments, early ones mostly interest. Extra payments go straight to principal, which shortens the loan and cuts interest; adjustable rates, escrow changes and prepayment penalties are not modelled.
Assumptions and limitations
- The limits are editable guidelines
- Excludes mortgage insurance and HOA dues
Estimates only. Taxes, fees and lender or authority rules vary by place and date, so confirm figures with the relevant authority or professional.
If a required value is empty, not a number, or outside its allowed range, the form marks that field with a message and shows no result instead of a misleading number. The automated checks deliberately try invalid entries for other monthly debt payments and annual gross income to confirm this.
Frequently asked questions
Is the 28/36 rule a requirement?
No, it is a guideline; lenders set their own limits.
Does a larger down payment help?
Yes, it increases the price you can afford for the same monthly payment.
Are closing costs included?
No. Closing costs are one-off and are not part of the monthly payment limit.
What does the House Affordability Calculator calculate?
Estimate the most expensive home your income supports. It returns Estimated maximum home price, Loan amount and Maximum monthly payment.
What formula does the House Affordability Calculator use?
PITI limit = min(front × income ÷ 12, back × income ÷ 12 − other debts); price solves payment(price − down) + price × tax ÷ 12 = limit. 28% and 36% are common guidelines and are editable; lenders set their own limits.
What do I need to enter in the house Affordability Calculator?
You enter Annual gross income ($), Other monthly debt payments ($), Down payment ($), Mortgage rate (%), Term (years), Housing payment limit (of gross income) (%), Total debt limit (of gross income) (%) and Property tax + insurance (of price, per year) (%).
How is the result rounded or limited?
IEEE-754 double precision; money shown to cents, rates to 4 decimals. Results are estimates, not financial advice. The limits are editable guidelines.
What are the limits of this calculator?
The limits are editable guidelines. Excludes mortgage insurance and HOA dues.
What is an example of a house Affordability result?
With annual gross income 90000, other monthly debt payments 500, down payment 40000, mortgage rate 6.5 and term 30, the estimated maximum home price is $310,781.48.
Can I rely on this calculator for a decision?
Estimates only. Taxes, fees and lender or authority rules vary by place and date, so confirm figures with the relevant authority or professional. For this calculator in particular: The limits are editable guidelines.
Related calculators
- Down Payment Calculator — Down payment amount and loan size from a percentage.
- Refinance Calculator — Monthly savings and break-even time from refinancing.
- APR Calculator — Annual percentage rate of a loan once upfront fees are counted.
- Amortization Calculator — Full amortization schedule with optional extra monthly payments.
- Mortgage Calculator — Monthly mortgage payment with property tax, insurance and HOA.
- VA Mortgage Calculator — Monthly payment with a financed funding fee you enter.
- Canadian Mortgage Calculator — Monthly payment with semi-annual compounding of the quoted rate.
- House Flipping Profit Calculator — Profit and return on cost of a renovate-and-sell project.
Sources
- Standard time-value-of-money relations (e.g. Brealey, Myers & Allen, Principles of Corporate Finance)
Content last reviewed 2026-11-04. Formulas and worked examples are checked by automated tests against independently computed values.