เครื่องคำนวณความสามารถในการซื้อบ้าน – ฉันซื้อบ้านราคาเท่าไรได้?
Find out how much home you can afford based on your annual income, down payment savings, monthly debts, and current mortgage rates. Our calculator uses the industry-standard 28/36 rule and shows your realistic price range.
วิธีใช้เครื่องคิดเลขนี้
- ป้อนAnnual Gross Income (฿)
- ป้อนDown Payment (฿)
- ป้อนMonthly Debt Payments (฿)
- ป้อนMortgage Interest Rate (%)
- ป้อนLoan Term (years)
- คลิกปุ่มคำนวณ
- อ่านผลลัพธ์ที่แสดงด้านล่างเครื่องคิดเลข
The 28/36 Rule Explained
The 28/36 rule is the cornerstone of mortgage affordability. It states: spend no more than 28% of gross monthly income on housing costs (front-end ratio) and 36% of gross monthly income on total debt (back-end ratio).
Housing costs in the 28% rule include: mortgage principal + interest + property taxes + homeowner's insurance (PITI) + HOA fees + PMI if applicable.
Example: Income ฿3,500,000/year = ฿291,655/month. Max PITI = ฿291,655 × 0.28 = ฿81,655. Max total debt = ฿291,655 × 0.36 = ฿105,000.
With ฿17,500 in existing monthly debts, you have ฿105,000 − ฿17,500 = ฿87,500 available for housing — limited by the back-end rule to ฿87,500 (not the ฿81,655 front-end maximum in this case).
Down Payment Impact on Affordability
Your down payment dramatically affects what you can afford and what you pay:
| Down Payment % | PMI Required? | Monthly Cost Impact | Upfront Cash Needed (฿14,000K home) |
|---|---|---|---|
| 3% (FHA) | Yes (MIP, permanent) | +฿7,000–400/mo | ฿420,000 |
| 5% | Yes (~0.5-1.5%/yr) | +฿5,250–300/mo | ฿700,000 |
| 10% | Yes (lower rate) | +฿2,625–150/mo | ฿1,400,000 |
| 20% | No | ฿0.00 | ฿2,800,000 |
PMI (Private Mortgage Insurance) typically costs 0.5–1.5% of the loan amount annually. On a ฿12,250,000 loan at 1%, that's ฿122,500/year or ฿10,220/month — a significant chunk of housing budget.
Mortgage Rate Impact on Affordability
Interest rates have a massive effect on home buying power. For a ฿14,000,000 home with 20% down (฿11,200,000 loan):
| Interest Rate | Monthly P&I | Total Interest Paid |
|---|---|---|
| 4.0% | ฿53,445 | ฿8,040,760 |
| 5.0% | ฿60,130 | ฿10,448,235 |
| 6.0% | ฿67,165 | ฿12,979,015 |
| 7.0% | ฿74,515 | ฿15,628,060 |
| 8.0% | ฿82,180 | ฿18,393,305 |
A 1% rate increase on a ฿11,200,000 loan adds ~฿7,000/month to your payment. This is why refinancing (or buying when rates are lower) saves hundreds of thousands over a 30-year loan.
Hidden Costs of Homeownership
First-time buyers often underestimate true homeownership costs beyond the mortgage payment:
- Property taxes: Typically 0.5–2.5% of home value annually (฿70,000–฿350,000+ on a ฿14,000K home)
- Homeowner's insurance: ฿28,000–฿70,000/year depending on location and coverage
- Maintenance and repairs: Budget 1–2% of home value annually (฿140,000–฿280,000 on a ฿14,000K home)
- HOA fees: ฿3,500–฿35,000+/month for condos and planned communities
- Utilities: Higher than renting — ฿7,000–฿21,000/month for a house vs. apartment
- Closing costs: 2–5% of purchase price (฿280,000–฿700,000 on a ฿14,000K home)
The true monthly cost of homeownership is often 25–40% higher than the mortgage payment alone. Factor these into your budget before committing.
How Lenders Calculate Maximum Loan Amount
Lenders use both DTI ratios and loan-to-value (LTV) ratios to determine maximum mortgage amounts. The lower of these two limits applies:
- Income-based limit: Maximum monthly payment × 12 months / annual rate factor
- Property-based limit: Appraised value × maximum LTV (typically 80% without PMI, 95–97% with PMI or FHA)
Credit score also affects the maximum loan. With a 620 credit score, you may only access FHA financing with a higher rate. A 760+ score unlocks the best conventional rates and more flexible terms.
First-Time Homebuyer Programs
If you're a first-time buyer (or haven't owned a home in 3 years), you may qualify for assistance:
- FHA loans: 3.5% down with 580+ credit score; 10% down with 500–579
- USDA loans: 0% down for rural/suburban properties; income limits apply
- VA loans: 0% down for eligible veterans and service members; no PMI
- State/local programs: Down payment assistance grants of ฿175,000–฿875,000+ in many states
- Good Neighbor Next Door: 50% off for teachers, law enforcement, firefighters, EMTs in HUD-designated areas
Rent vs. Buy: When Does Buying Make Sense?
Use the price-to-rent ratio (P/R) to decide: P/R = Home Price ÷ Annual Rent. Below 15: buying is clearly better. 15–20: depends on personal factors. Above 20: renting may be financially smarter.
Other factors favoring buying: plan to stay 5+ years, stable income, building equity/wealth, desire to customize, tax benefits (mortgage interest deduction for itemizers). Factors favoring renting: need flexibility, market at peak, high maintenance costs, better investment opportunities elsewhere.
อัปเดตล่าสุด: March 2026
Frequently Asked Questions
How much house can I afford on ฿2,100,000 a year?
On ฿2,100,000/year (฿175,000/month), the 28% rule gives ฿49,000/month for housing (PITI). At a 7% rate with 20% down, this translates to roughly ฿6,125,000–฿7,000,000 purchase price depending on taxes and insurance in your area.
How much house can I afford on ฿3,500,000 a year?
฿3,500,000/year = ฿291,655/month. Max PITI at 28% = ฿81,655/month. At 7% for 30 years with 20% down, this supports approximately ฿10,150,000–฿11,550,000 in purchase price.
What credit score do I need to buy a house?
Minimum: 500 (FHA with 10% down). Practical minimum: 620 for most conventional loans. Best rates: 740–760+. Each 20-point improvement in credit score can improve your rate by 0.25–0.5%, saving tens of thousands over the loan life.
How much do I need for a down payment?
Minimum: 3% conventional, 3.5% FHA, 0% VA/USDA. Recommended: 20% to avoid PMI. On a ฿12,250,000 home, 20% = ฿2,450,000. Many buyers use 5–10% and accept PMI to buy sooner.
Is it better to get pre-qualified or pre-approved?
Pre-approval is better. Pre-qualification is a quick estimate based on self-reported data. Pre-approval involves verified income, credit pull, and asset verification — it's a conditional commitment from a lender and strengthens your offer.
What is the rule of thumb for home affordability?
The most common rules: (1) 28/36 rule — PITI ≤28% of gross income, total debts ≤36%. (2) 2.5–3x income rule — home price ≤ 2.5–3× annual gross income. Both are starting points; adjust for local market conditions.
How does student debt affect home buying?
Student loans count as monthly debt payments in DTI calculations. Even in deferment, lenders typically count 0.5–1% of the balance as a monthly payment. High student debt significantly reduces maximum mortgage amount.
Can I buy a house with no down payment?
Yes, through VA loans (veterans), USDA loans (rural areas), or some state/local first-time buyer programs. No-down-payment loans result in higher monthly payments and immediate negative equity if the market drops.
What is included in a mortgage payment?
A full mortgage payment (PITI) includes: Principal (loan repayment), Interest, property Taxes (escrowed), and homeowner's Insurance (escrowed). May also include PMI, HOA fees, and flood insurance.
How do I get the best mortgage rate?
Key factors: credit score (760+ for best rates), down payment (20%+ for no PMI), loan type (conventional vs. FHA), loan amount, and lender competition. Shop at least 3–5 lenders and consider mortgage brokers who access multiple wholesale lenders.