Free Mortgage Calculators: Affordability, Payment and Costs

Buying a home involves three distinct numerical questions that most people cannot answer accurately without a calculator: Can I actually afford this? What will my monthly payment be, including taxes and insurance? And what does this loan cost over 30 years — not just the monthly payment, but the total interest paid? The gap between what people think they can afford and what the math says is usually significant, in both directions.

This guide walks through the free calculators that answer each question concretely, with worked examples. None require an account or store your data. The full set is in the Calculators hub.

Step 1: How Much House Can You Actually Afford?

Lenders use the 28/36 rule as a standard underwriting guideline. The front-end ratio says your total monthly housing costs — principal, interest, taxes, and insurance (PITI) — should not exceed 28% of your gross monthly income. The back-end ratio says all monthly debt payments combined (housing plus car loans, student loans, credit cards) should not exceed 36% of gross monthly income.

The Mortgage Affordability Calculator applies this rule to your specific numbers and tells you exactly how much house you can afford. Here is a concrete example: a household with $85,000 in gross annual income ($7,083/month) and $400/month in existing debt payments (car loan + student loan).

• Front-end limit (28%): $7,083 × 0.28 = $1,983/month maximum housing payment
• Back-end limit (36%): $7,083 × 0.36 = $2,550 − $400 existing debt = $2,150/month maximum housing payment
• The binding constraint is the lower figure: $1,983/month
• At a 7% rate on a 30-year mortgage with $40,000 down, this translates to a maximum home price of approximately $285,000

Notice how pre-existing debt reduces buying power: without the $400 monthly debt, the back-end limit would have been $2,550, allowing a home price closer to $340,000. Every dollar of monthly debt you carry into a home purchase costs you roughly $140 in home-buying capacity at current rates.

Before running the affordability calculator, use the Paycheck Calculator to confirm your actual take-home pay — your gross income is what lenders use for the 28/36 rule, but your take-home pay is what you actually live on and what the mortgage payment has to fit inside. The gap between gross and net can be 25–35% once federal tax, FICA, and benefits deductions are accounted for. And use the Tax Bracket Calculator to understand how a home purchase (and the mortgage interest deduction, if you itemize) might shift your tax picture.

Step 2: What Is the Actual Monthly Payment?

The monthly payment quote you typically see advertised is the principal and interest (P&I) component only — often the lowest number a lender can legally show you. Your real monthly obligation is PITI: Principal + Interest + Taxes + Insurance. In most markets, property taxes and homeowners insurance together add $300–600/month to the payment shown in the headline rate.

The Mortgage Calculator includes property taxes, homeowners insurance, and PMI (private mortgage insurance, required when your down payment is under 20%) so you see the true PITI from the start. A concrete example:

• Home price: $280,000, down payment: $40,000 (14.3% — PMI applies)
• Loan amount: $240,000 at 7% for 30 years
• Principal & Interest: $1,597/month
• Property tax (est. 1.2% annually): $280/month
• Homeowners insurance (est. 0.6% annually): $140/month
• PMI (est. 0.6% of loan): $120/month
• Total PITI: $2,137/month

The difference between the advertised $1,597 and the actual $2,137 is $540/month — $6,480/year. PMI cancels once your equity reaches 20% (around year 8 at standard amortization pace), which is when monthly costs drop by $120 automatically. The mortgage calculator shows exactly when that happens and what the payment looks like afterward.

Step 3: What Does This Loan Actually Cost Over 30 Years?

The total cost of a mortgage is the number almost nobody calculates before signing — because it is shocking. On the $240,000 loan from the example above at 7% over 30 years:

• Total of 360 payments: $1,597 × 360 = $574,920
• Total interest paid: $574,920 − $240,000 = $334,920
• You pay back more than twice what you borrowed

The Loan & EMI Calculator shows the full amortization table — every payment for all 360 months, broken down between principal and interest. The first payment on this loan sends $997 to interest and only $600 to principal. It takes roughly 19 years before the monthly payment tips to more principal than interest.

One important counterpoint: a fixed-rate mortgage is one of the few debts that becomes cheaper in real terms over time. The Inflation Calculator shows what $1,597 in 2026 is worth in future dollars. At a 2.5% average inflation rate, that $1,597 payment has the purchasing-power equivalent of about $970 in today's dollars by 2046. Your income likely grows with inflation; your fixed mortgage payment does not.

For borrowers who want to reduce total interest, running the loan calculator with an extra $100–200/month principal payment shows the impact clearly: an extra $200/month on this loan eliminates 7 years of payments and saves nearly $80,000 in interest over the life of the loan.

Step 4: Saving for the Down Payment

A 20% down payment on a $280,000 home requires $56,000 — before closing costs, which typically add another 2–5% of the purchase price ($5,600–$14,000). The total cash needed to close is often $65,000–$70,000 even at the 20% threshold.

The Savings Goal Calculator works backwards from a target to a required monthly savings amount. To save $60,000 in four years earning 4.5% in a high-yield savings account:

• Monthly contribution required: approximately $1,080/month
• Total contributed over 4 years: $51,840
• Interest earned: $8,160
• Final balance: $60,000

If $1,080/month is out of reach, the calculator lets you adjust the timeline — extend to 5 years and the monthly requirement drops to approximately $840. The Compound Interest Calculator models the same scenario with different contribution amounts and compounding frequencies, useful for comparing a high-yield savings account versus a conservative investment account for the down payment fund.

Note that putting less than 20% down does not necessarily mean waiting longer to buy — it means paying PMI until you reach 20% equity. At $120/month, PMI on the example above costs $1,440/year. Whether it is cheaper to pay PMI for 8 years ($11,520 total) versus saving an additional $16,000 in down payment before buying depends on the local market and your timeline. The mortgage affordability calculator makes both scenarios comparable in minutes.

Step 5: How Existing Debt Affects Your Options

Debt-to-income ratio is the single most common reason first-time buyers qualify for less than they expected. Every $100 in monthly debt payments reduces mortgage affordability by approximately $14,000 in home price at current rates. A buyer carrying $700/month in car loan + student loan payments is effectively pre-spending $98,000 of their borrowing capacity before the conversation with a lender even begins.

The Debt Payoff Calculator shows two strategies — debt avalanche (highest interest rate first) and debt snowball (smallest balance first) — and compares the total interest and time to payoff for each. For a prospective buyer targeting a home purchase in 18–24 months, eliminating specific debts in the right order can meaningfully increase their qualified loan amount.

A practical example: a buyer with an $8,000 credit card balance at 22% APR and a $5,000 car loan at 6% APR, paying $400/month toward both. The debt calculator shows the avalanche method pays both off in 35 months saving $1,200 in interest over the snowball method. More importantly, eliminating the $250/month credit card minimum payment removes $35,000 from the buyer's effective debt load in the affordability calculation — worth more than the interest savings.

Running the Numbers as a System

Home buying math is not one calculation — it is a chain where each output feeds the next. A practical sequence:

1. Use the Paycheck Calculator to find your actual monthly take-home income — and understand how it differs from your gross income, which lenders use.
2. Use the Mortgage Affordability Calculator with your gross income and current monthly debts to set a realistic price ceiling — before you start browsing listings.
3. Use the Mortgage Calculator on specific listings to see the full PITI payment, not just the P&I. Confirm the PITI fits your take-home budget with room for maintenance, utilities, and savings.
4. Use the Loan Calculator to see the full amortization schedule — total interest over the loan term, and what happens if you pay an extra $100–300/month.
5. Use the Savings Goal Calculator to build a monthly savings plan for the down payment and closing costs, and the Debt Payoff Calculator to clear the debts most damaging to your DTI ratio before applying.

Running this sequence before talking to a lender means you walk in knowing your actual numbers — not surprised by them. It also means you can evaluate whether a specific home at a specific price makes sense for your situation without waiting for a bank's pre-approval to tell you.

Frequently Asked Questions

How much house can I afford on a $70,000 salary?
At $70,000 gross annually ($5,833/month), the 28% front-end limit is $1,633/month for PITI. At 7% for 30 years with a 10% down payment and $250/month in existing debt obligations (back-end limit: $5,833 × 0.36 − $250 = $1,850), the binding constraint is the front-end. This translates to approximately $220,000–$230,000 in home price depending on local property tax rates and insurance. The Mortgage Affordability Calculator runs this with your exact inputs.

What is the 28/36 rule?
The 28/36 rule is a lender guideline: spend no more than 28% of gross monthly income on housing costs (PITI) and no more than 36% on all debt payments combined. It is not a law — lenders can and do approve loans above these ratios, particularly with strong credit and significant down payments — but exceeding the ratios usually means a higher interest rate or additional scrutiny.

How much do I need for a down payment?
Conventional loans require a minimum of 3–5% down. FHA loans require 3.5%. VA and USDA loans offer 0% down for eligible borrowers. Putting less than 20% down triggers PMI on conventional loans, typically 0.5–1% of the loan amount annually. The practical minimum for most first-time buyers to avoid significant PMI cost is 10–20%, though the right amount depends on your market, timeline, and opportunity cost of keeping cash invested.

What does PITI stand for?
PITI stands for Principal, Interest, Taxes, and Insurance — the four components of a complete monthly mortgage payment. Principal is the portion reducing the loan balance. Interest is the lender's charge on the outstanding balance. Taxes are property taxes, typically collected monthly into an escrow account by the lender. Insurance includes homeowners insurance and PMI if applicable. PITI is the figure lenders use for the 28% front-end ratio calculation.

Should I pay off debt before buying a house?
It depends on which debt and how much. High-interest revolving debt (credit cards at 20%+ APR) almost always makes sense to pay off first — the interest cost exceeds mortgage rates and it directly harms your DTI ratio and credit score. Low-interest installment debt (car loans at 4–6%, student loans at 5–7%) may not be worth aggressive payoff if eliminating it delays your home purchase for several years in a rising market. The Debt Payoff Calculator helps model both scenarios with specific balances and rates.

All the calculators referenced in this guide are free, work entirely in your browser, and require no account. Find the full set — mortgage, loan, savings, paycheck, tax bracket and more — in the Calculators hub, or browse all 130+ tools at the Nutilz homepage.