Reallocated Sector Count: What It Means and When to Worry

You ran CrystalDiskInfo or another SMART tool and saw a yellow Caution next to Reallocated Sectors Count. Here’s exactly what that number means, how worried to be, and what to do.

What a reallocated sector is

A hard drive’s platters are divided into millions of tiny sectors, each holding a small block of data. Every drive also ships with a reserve pool of spare sectors.

When the drive finds a sector it can no longer read or write reliably, it remaps that location to a spare. Your computer never sees the bad spot again — the drive quietly redirects to the replacement. SMART attribute 05 (Reallocated Sectors Count) counts how many times that has happened.

In other words: every reallocated sector is a piece of the disk surface that has already failed.

How to read the number

SMART tools show each attribute two ways:

• Raw value — the actual count of reallocated sectors. This is the one to watch.
• Normalized value / threshold — a 1–100 (or 1–253) health score the drive calculates. When the normalized value drops to the threshold, the drive reports a SMART failure.

Don’t wait for the normalized value to hit the threshold. By then, the drive is usually in serious trouble.

When to worry

Large-scale drive-reliability data (Backblaze publishes statistics from hundreds of thousands of drives) identified Reallocated Sectors Count as one of a handful of SMART attributes most strongly linked to failure. A practical way to read it:

• 0 — ideal.
• A small, stable number that hasn’t changed in months — keep an eye on it, and make sure your backup is current.
• A number that’s growing — the surface is actively degrading. Back up now and plan to replace the drive.
• Any reallocated sectors plus pending or uncorrectable sectors — treat the drive as failing. See Current Pending Sector Count.

The trend matters more than the number. Check again in a week; if it climbed, the drive is running out of road.

Related attributes to check

• 196 – Reallocation Event Count: how many remapping events have occurred.
• 197 (C5) – Current Pending Sector Count: sectors that can’t currently be read and are waiting to be remapped. Data in those sectors may already be unreadable.
• 198 (C6) – Uncorrectable Sector Count: sectors that failed even after retries.
• 187 (BB) – Reported Uncorrectable Errors.

For a full walkthrough, see how to check hard drive health.

What to do now

1. Back up your most important files first. Not a full clone — your irreplaceable files, right now.
2. Avoid stress. Skip defragmenting, long surface scans, chkdsk /r, and “sector repair” tools. They force the drive to read every sector, including the weak ones, and can accelerate failure.
3. Replace the drive. A drive with a growing reallocated count shouldn’t hold the only copy of anything.
4. Clone carefully if you need everything. If you must copy the whole drive, use imaging software that skips unreadable areas and returns to them last, rather than a standard copy that stalls and retries.

When it’s past DIY

If the drive is already slow, freezing, clicking, or failing to copy files, or the reallocated count is climbing fast alongside pending sectors, stop. Professional recovery uses hardware imagers that control exactly how the drive is read — reading healthy areas first, limiting retries on weak ones, and protecting the heads — which preserves far more data than a normal copy.

The bottom line

Reallocated Sectors Count tells you how much of the disk has already failed and been patched. Zero is ideal; a growing number means the drive is degrading. Back up now, avoid heavy scans, and replace the drive before it decides for you.

If the drive is already struggling to give your data back, our hard drive recovery service images degrading drives safely for one flat price — and you pay nothing unless we succeed.