Understanding Zillow Comps and How to Run Your Own Analysis

Comparable sales, or comps, are how agents and appraisers judge a home's value: recent sales of similar homes nearby. You can run a solid rough version yourself on Zillow in about 20 minutes. Here's the method.

Step 1: pull up recently sold homes

1. Search the neighborhood on Zillow and switch the listing type from For Sale to Sold.
2. Set the sold date to the last three to six months. In a fast market, use the shortest window that still gives you a few results.
3. Draw a boundary on the map around the immediate area, ideally within about half a mile, and on the same side of any big divider like a highway, rail line, or school boundary.

Step 2: filter to real comparables

• Same home type: house with house, condo with condo.
• Similar size: within about 20 percent of the target's square footage.
• Similar beds and baths, and roughly similar age.
• Normal sales only. Leave out foreclosures and auctions, which sell at a discount for other reasons.

Aim for three to six good comps rather than many loose ones.

Step 3: compare and adjust

No two homes match exactly. For each comp, note what's better or worse than your target: an extra bathroom, a garage, a renovated kitchen, a pool, a smaller lot, or a busy street. Your target's value should land above comps it beats and below comps that beat it. Photos and descriptions tell you about condition, which often matters as much as size.

Step 4: use price per square foot

1. Divide each comp's sale price by its square footage.
2. Look at the range and the middle of it.
3. Multiply your target's square footage by that middle figure for a rough value, then nudge it up or down for the differences you noted.

Zillow Price/SqFt shows price per square foot on every listing card, which makes scanning sold homes much faster, and the price per square foot calculator handles the math. Keep in mind that smaller homes usually sell for more per square foot than larger ones, so compare similar sizes.

Where the Zestimate fits

The Zestimate is Zillow's automated estimate, built from similar data. It's a useful sanity check, but it can't see condition, upgrades, or what's special about a street, and Zillow's own published error rates are higher for homes that aren't on the market. Your own comps, and an agent's, are more reliable.

Common mistakes

• Using active listings as comps. Asking prices aren't sale prices.
• Reaching too far away or too far back to find more comps.
• Ignoring condition. A renovated home and a dated one on the same street can sell far apart.
• Forgetting that sale records lag, so the newest sales may not show yet.

When to bring in a pro

Agents can see more complete local sales data, and a lender relies on an appraisal, not your comps. Use your analysis to judge listings and make a sensible offer, then let your agent check it. For reading a single listing, see what Zillow price history tells you.