Rent affordability calculator

What is a rent affordability calculator?

A rent affordability calculator is a free tool that estimates the highest monthly rent you can comfortably carry based on what you earn and what you already owe. Instead of guessing whether a listing fits your budget, you enter your gross monthly income, your other monthly debt payments, and the share of income you want to spend on rent. The calculator then returns a target rent figure, a ceiling set by a common debt-to-income guideline, and a single recommended maximum that respects both. Seeing all three numbers at once helps you shop for an apartment with a firm limit in mind rather than falling in love with a place you cannot sustain.

How does it work?

You supply three values. The first is your gross monthly income, meaning your pay before taxes and deductions. Lenders and landlords almost always work from gross figures, so the calculator does too. The second is your other monthly debt payments, such as a car loan, student loan, or minimum credit card payments; leave it at zero if you have none. The third is your target rent-to-income ratio, expressed as a percentage, which lets you tune the classic 30% guideline up or down to match your own comfort level.

From these inputs the calculator works out two independent limits. The first limit applies your chosen ratio directly to your income. The second limit applies the 28/36 rule: it caps your total monthly debt obligations, rent included, at 36% of gross income, then subtracts your existing debt payments to see what room is left for rent. The recommended maximum is simply the smaller of the two, because a rent you can afford has to satisfy both tests at the same time. If your debt payments are high enough that the 36% ceiling is already used up, the debt-rule limit falls to zero rather than turning negative.

The 30% rule is the rule of thumb most people know: housing costs should stay at or below 30% of gross income. The 28/36 rule is the more complete standard that lenders use. The 28 refers to housing alone staying under 28% of gross income, while the 36 says that total debt payments, including housing, should stay under 36% of gross income. This calculator focuses on that 36% total-debt ceiling because it is the constraint that accounts for the other loans you are already paying.

Formula

Let $I$ be gross monthly income, $D$ your other monthly debt payments, and $p$ your target rent-to-income ratio as a percentage.

The rent implied by your target ratio is:

$R_\text{income} = I \times \frac{p}{100}$

The rent allowed by the 36% total-debt rule is the 36% ceiling minus what you already owe, floored at zero:

$R_\text{debt} = \max\left(0,\; 0.36 \times I - D\right)$

The recommended maximum rent is the lower of the two limits:

$R_\text{max} = \min\left(R_\text{income},\; R_\text{debt}\right)$

Worked example

Suppose you earn $5,000 a month before taxes, you already pay $500 a month toward a car loan and other debts, and you want to keep rent at 30% of income.

The target-ratio limit is $5000 \times 0.30 = 1500$, so $1,500.

The debt-rule limit is $\max(0,\; 0.36 \times 5000 - 500) = \max(0,\; 1800 - 500) = 1300$, so $1,300.

The recommended maximum is $\min(1500, 1300) = 1300$, so $1,300. Here the existing car payment is the binding constraint: even though the 30% rule alone would allow $1,500, staying under the 36% total-debt ceiling pulls the safe figure down to $1,300.

If you had no other debt, the debt-rule limit would rise to $0.36 \times 5000 = 1800$, and the 30% rule at $1,500 would then be the tighter of the two, making $1,500 the recommended maximum.

Notes

These figures are guidelines, not hard rules. High earners can often spend a smaller share of income on rent while still living comfortably, and people in expensive cities sometimes stretch beyond 30% by trimming other spending. The calculator uses gross income because that is the standard basis for these rules, but your take-home pay after taxes and retirement contributions is what actually funds the rent, so treat the output as a ceiling rather than a target.

Rent is also only part of housing cost. Renters insurance, utilities, parking, and pet fees add up, and they are not captured here. Build a little headroom below the recommended maximum so that these extras, plus savings and unexpected bills, still fit your budget. The chart breaks your gross monthly income into three slices — recommended rent, other debt payments, and what is left over — so you can see at a glance how much room the rest of your budget has.

FAQs

Should I use gross or net income?

Use gross income, your pay before taxes and deductions. The 30% and 28/36 rules were designed around gross figures, and that is what most landlords and lenders check. Just remember that your actual spendable income is lower, so leave yourself margin.

What counts as other monthly debt payments?

Include recurring obligations such as car loan payments, student loan payments, personal loan payments, and the minimum payments on credit cards. You do not need to include everyday expenses like groceries or streaming subscriptions, since the 36% rule is about debt, not general spending.

Why is my recommended rent lower than 30% of my income?

Because the recommended maximum also respects the 36% total-debt ceiling. When you already have significant loan payments, those payments eat into the 36% allowance, leaving less room for rent than the 30% rule alone would suggest. The calculator always reports the smaller, safer of the two limits.