Home Value Calculator (US)

Estimate a home's market value with the sales comparison approach: start from a comparable sale's price per square foot, scale it to your home's size, then add a net dollar adjustment for condition, bed/bath count, and other differences.

Quick Facts

Formula
Value = (Comp price / Comp sq ft) × Your sq ft + Net adjustment
The standard sales comparison approach used in real estate appraisal.
Comp count
More comparables narrow the estimate
Appraisal guidelines typically call for at least 3 comparable sales.

Your Results

Calculated
Estimated home value
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Size-adjusted comp price + net adjustment
Comp price per sq ft
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Comparable sale price ÷ comparable size
Size adjustment
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Value added or subtracted for size difference
Implied price per sq ft
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Estimated value ÷ your home's size

Ready

Enter a comparable sale, both square footages, and your net adjustment, then press Calculate.

How the Home Value Calculator (US) works

This tool estimates a home's market value using the sales comparison approach — the same core method licensed appraisers and real estate agents use to price a home against recent nearby sales. Instead of guessing, it scales a comparable sale's price per square foot to your home's size, then applies a net dollar adjustment for the differences a size-only comparison can't capture, such as condition, bedroom or bathroom count, garage space, or lot size.

The formula

For a comparable sale price Pcomp, comparable size SqFtcomp, your home's size SqFtsubject, and a net feature adjustment A (positive if your home has more value-adding features than the comp, negative if fewer), the estimate is:

Estimated Value = (Pcomp / SqFtcomp) × SqFtsubject + A

The first term — comp price per square foot times your square footage — captures the size-driven part of value. The net adjustment then layers on everything the comp's size alone doesn't explain: a renovated kitchen, an extra bathroom, a bigger garage, a better or worse lot, or general condition differences. Because that adjustment is a single number you supply, you control how it's built — add and subtract individual line items separately before entering the total if you want a transparent paper trail.

Worked example

A comparable home sold for $420,000 at 1,800 sq ft, giving a price per square foot of $420,000 / 1,800 ≈ $233.33. Your home is 2,100 sq ft, so the size-adjusted value is $233.33 × 2,100 ≈ $490,000 — that's $70,000 more than the comp purely from the extra 300 square feet. Add a net feature adjustment of $12,000 (say, for an updated bathroom you have and the comp doesn't) and the estimated value comes to about $502,000, or roughly $239.05 per square foot on your home.

Choosing a good comparable

  • Recency: use a sale from the last 3-6 months where possible — older sales may not reflect current market conditions.
  • Proximity: a comp in the same neighborhood or school zone is more reliable than one across town.
  • Similarity: the closer the comp is in size, age, and style, the smaller (and more defensible) your net adjustment needs to be.
  • Multiple comps: professional appraisals typically draw on at least three comparable sales and reconcile the results rather than relying on a single data point — averaging two or three independent estimates from this calculator with different comps will narrow your range.

What this calculator does not do

This is a simplified, transparent version of the sales comparison approach — it does not access live listing data, does not automatically select or weight comparables, and does not replace a licensed appraisal, a comparative market analysis from a real estate agent, or an automated valuation model. Use it to sanity-check a number or to understand how comp price, size, and adjustments interact, not as a substitute for a professional valuation when money is on the line (financing, listing, refinancing, or a property tax appeal).

Frequently Asked Questions

What is the sales comparison approach?
It's the standard real estate valuation method that estimates a home's value by starting from recent sale prices of similar nearby homes ("comparables" or "comps") and adjusting for differences in size, condition, and features. This calculator implements a simplified version: it scales a comp's price per square foot to your home's size, then adds a net dollar adjustment you supply for the remaining differences.
How do I come up with the net feature adjustment number?
Add up the dollar value of features your home has that the comp lacks (an extra bathroom, a finished basement, a newer roof), then subtract the value of features the comp has that your home lacks. If your home is worth more than the comp for reasons beyond square footage, enter a positive number; if less, enter a negative number. Many users build this total from a handful of line items priced separately, then enter the sum.
Why does the comp's price per square foot matter so much?
It's the multiplier applied to your entire square footage, so a small error in the comp's price or size gets magnified. A comp priced or measured incorrectly by 5% can shift a 2,000 sq ft estimate by tens of thousands of dollars. Double-check the comp's actual sale price (not list price) and its square footage from a reliable source, such as a listing record or public assessor data.
Why does the calculator ask how many comparable sales I used?
The comparable count doesn't change the arithmetic — it's used to flag how much confidence to place in a single run. One comp gives a rough estimate; appraisers typically reconcile three or more independent comps to reduce the influence of any single unusual sale. Run this calculator once per comp and compare the results to see how much your estimate moves.

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