Comps Calculator

Estimate a property’s market value using comparable sales data.

Subject Property

Comparable Properties (Comps)

Enter details for 2-3 recently sold properties that are similar to the subject property. Adjustments help account for differences between the comp and your property.

Comparable Property 1

Comparable Property 2

Comparable Property 3

Estimated Market Value

$0

Adjusted Comp 1$0

Adjusted Comp 2$0

Adjusted Comp 3$0

Avg. Adjusted Price / sq ft$0

Formula Explanation: The estimated value is the average of the “Adjusted Prices” of the comparable properties. Each comp’s sale price is adjusted up or down based on how its features (beds, baths, etc.) compare to the subject property, plus any manual adjustments for condition or location.

Value Comparison Chart

Comps Summary Table

Metric	Comp 1	Comp 2	Comp 3
Sale Price	$0	$0	$0
Adjustments	$0	$0	$0
Adjusted Price	$0	$0	$0
Price / sq ft	$0	$0	$0

What is a Comps Calculator?

A comps calculator is a tool used in real estate valuation to estimate the market value of a property. “Comps” is short for comparables, which are recently sold properties that are similar to the property you are valuing (the “subject property”). By analyzing the sale prices of these comps and making adjustments for differences in features, location, and condition, you can arrive at a highly educated estimate of what the subject property is worth in the current market. This process is a cornerstone of a Comparative Market Analysis (CMA).

This calculator is essential for home sellers trying to set a competitive asking price, buyers wanting to make an informed offer, and real estate investors analyzing potential deals. It formalizes the process that appraisers and real estate agents use every day.

Comps Calculator Formula and Explanation

The core of a comps calculator isn’t a single formula, but an adjustment process. The value of the subject property is inferred from what buyers were willing to pay for similar properties. The main formula is for the adjusted value of each comp:

Adjusted Comp Price = Comp Sale Price + Total Adjustments

Total Adjustments are calculated by assigning a dollar value to each major feature difference between the subject and the comp. If the subject is superior, you add value to the comp’s price. If the comp is superior, you subtract value.

Estimated Market Value = Average of all Adjusted Comp Prices

Formula Variables

Variable	Meaning	Unit	Typical Range
Comp Sale Price	The price a comparable property recently sold for.	Currency ($)	Varies by market
Feature Adjustment	Value assigned to a specific feature difference (e.g., a bedroom or bathroom).	Currency ($)	$5,000 – $30,000
Manual Adjustment	Value for subjective differences like condition, view, or location.	Currency ($)	-10% to +10% of sale price
Adjusted Comp Price	The normalized value of a comp after all adjustments.	Currency ($)	Varies by market

Practical Examples

Example 1: Subject Property is Slightly Better

Imagine your house (Subject) has 3 beds, 2 baths, and is 2,000 sq ft. A comp sold for $500,000 but only had 2 baths and was in slightly worse condition.

• Inputs:
  • Comp Sale Price: $500,000
  • Subject Baths: 3, Comp Baths: 2 (Difference: +1)
  • Manual Adjustment for Condition: +$10,000 (because your house is better)
• Calculation:
  • Let’s assume a bathroom is worth $15,000.
  • Adjustment = (1 bath * $15,000) + $10,000 = +$25,000
  • Adjusted Comp Price = $500,000 + $25,000 = $525,000
• Result: This single comp suggests your home’s value is around $525,000.

Example 2: Subject Property is Inferior

Your house (Subject) is 2,000 sq ft. A comp sold for $550,000 and was 2,300 sq ft with a brand new kitchen, while yours is dated.

• Inputs:
  • Comp Sale Price: $550,000
  • Sq Ft Difference: 300 sq ft (Comp is larger)
  • Manual Adjustment for Kitchen: -$20,000 (because comp’s kitchen is superior)
• Calculation:
  • Assume price per sq ft is $250. Adjustment for size = 300 * $250 = $75,000. Since the comp is larger, this is a negative adjustment.
  • Total Adjustment = -$75,000 (for size) – $20,000 (for kitchen) = -$95,000
  • Adjusted Comp Price = $550,000 – $95,000 = $455,000
• Result: After adjusting for its superior size and kitchen, this comp suggests your home’s value is closer to $455,000. Performing a comparable market analysis with multiple properties provides the most accurate picture.

How to Use This Comps Calculator

1. Enter Subject Property Details: Start by inputting the square footage, and the number of bedrooms and bathrooms for the property you want to value.
2. Find Comparable Properties: Find at least 2-3 similar properties that have sold within the last 3-6 months and are located as close as possible (ideally within a 1-mile radius). Use real estate websites or consult an agent for this data.
3. Input Comp Data: For each comparable property, enter its final sale price, square footage, bed/bath count.
4. Make Adjustments: Use the “Manual Adjustment” field to account for qualitative differences. If the comp has a major flaw your home doesn’t (e.g., backs to a busy road), add a positive adjustment. If the comp has a superior feature (e.g., a new pool, a great view), add a negative adjustment. This is the art of understanding property value.
5. Review the Results: The calculator automatically provides the “Estimated Market Value” as the primary result. Pay attention to the intermediate values like the adjusted price for each comp and the average price per square foot to understand the valuation better.

Key Factors That Affect Comps Valuation

• Location: The most important factor. Comps should be from the same neighborhood or a very similar one. A mile can make a huge difference in value.
• Date of Sale: Markets change. A sale from one year ago is far less relevant than a sale from last month. Stick to sales within the last 6 months if possible.
• Square Footage: The overall size of the home is a primary driver of value. Try to use comps within 10-15% of the subject’s square footage.
• Bed & Bath Count: These are critical features for buyers. A 4-bedroom home is fundamentally different from a 2-bedroom home, even at the same square footage.
• Condition: Is the property newly renovated or in a state of disrepair? This requires subjective but crucial manual adjustments. This is key for any home value estimator.
• Lot Size & Usability: A larger or more usable yard, especially in suburban areas, can add significant value.

Frequently Asked Questions (FAQ)

What is a good comp?

A good comp is a property that is as similar as possible to your subject property, sold as recently as possible (ideally under 6 months), and is located as close as possible (ideally under 1 mile). Similarity includes style, age, size, and features.

How do I determine the value of an adjustment?

This is the most challenging part. You can estimate adjustment values by looking at paired sales (two similar sales where the main difference is one feature) or by using cost data (e.g., the cost to add a bathroom). Real estate agents often have standard adjustment values for their local market.

Can I use active listings as comps?

You can, but with caution. Active listings show the *asking* price, not the final sale price. They represent the competition but not the proven market value. Sold properties are much more reliable indicators for a comps calculator.

Why is my calculated value different from an online estimate?

Online estimators use automated models with vast data but may lack nuance. They might not know about your recent kitchen renovation or the comp’s water damage. A manual comps calculator like this one allows for specific, intelligent adjustments that automated models can miss.

How many comps should I use?

Three is the minimum for a reliable estimate. Using five or six, if available, can provide a more accurate and defensible valuation by smoothing out any single outlier.

What if I can’t find any good comps?

For unique properties or in rural areas, you may need to expand your search radius, go further back in time, or use comps that are less similar and make larger adjustments. This reduces the certainty of the valuation.

Is a Comparative Market Analysis (CMA) the same as an appraisal?

No. A CMA, which uses a comps calculator, is an estimate of value typically done by a real estate agent. An appraisal is a formal, legal opinion of value conducted by a state-licensed appraiser, often required for a mortgage.

How does Price Per Square Foot factor in?

Price per square foot is a useful secondary metric, but it can be misleading. Smaller homes often have a higher price per square foot than larger homes. It’s better to use the adjustment method, as this calculator does, and use price per square foot as a general guide.