Real Estate Math: How to Choose the Right Formula

Start with what the question asks you to find. Then identify the information needed for that result. Choosing the right relationship matters more than recognizing a familiar number.

A repeatable approach

1. Name the unknown. Write “commission,” “loan amount,” “total debt ratio,” or the exact result requested.
2. Label the facts. Separate price, rate, income, debt, area, and time. Identify facts that do not belong in this calculation.
3. Write the relationship in words. For example: part = whole × rate; rate = part ÷ whole.
4. Match the units. Do not divide monthly debt by annual income. Convert percentages to decimals when multiplying.
5. Calculate, then check. Estimate the result first and follow the question's rounding instructions.

Worked example: total debt-to-income ratio

This original practice example gives gross monthly income of $5,000, a proposed monthly housing payment of $1,800, and other counted monthly debt payments of $750. It asks for the total debt-to-income ratio.

Total monthly obligations = $1,800 + $750 = $2,550.
Total debt ratio = $2,550 ÷ $5,000 = 0.51 = 51%.

Using only $1,800 would produce a 36% housing ratio. That answers a different question. The word “total” tells you to include the other counted debts supplied in the example. This exercise practices calculation; it does not establish a lender's approval standard.

Try a fresh example

Gross monthly income is $6,000. The question states that total counted monthly obligations, including housing, are $2,100. What is the total debt ratio?

Answer: $2,100 ÷ $6,000 = 0.35 = 35%. Do not add the housing payment again if it is already included in the total.

When you miss a math question

Identify whether the error came from selecting the formula, choosing the numbers, converting units, entering the calculation, or rounding. Practice the same skill with new numbers after reviewing the explanation.

Use Read Exam Questions and Compare Answer Choices and Use Practice Results to Improve Your Exam Preparation to track the pattern. If you need help, send support the permitted practice problem and your calculation steps.