SSDs have replaced hard drives as the de facto standard for most use cases, but they're not perfect. Unlike hard drives, SSDs have a fixed lifespan due to the nature of flash storage. This lifespan is often communicated to the consumer using various ratings by the manufacturer, or you can use third-party tools to get a rough idea of your SSD health.

While most SSDs will probably last longer than most people will use them, you can estimate the remaining lifespan of your SSD if you're curious. There are mostly two ways to do this, and I'll get into each of them after discussing some basic stuff about the nature of flash memory.

Why does your SSD run out of life?

The nature of the beast

SSDs use flash memory cells to store data, and every single write reduces a cell's lifespan slightly. To tackle this, SSDs use "wear leveling," which essentially distributes the write operations across the drive's flash cells to evenly spread the wear and tear across the entire drive. Most modern SSDs do this by default; you don't need to do any manual intervention to enable it.

To give consumers an idea about an SSD's lifespan or endurance, manufacturers publish a metric called TBW or terabytes written. This translates to the number of TBs that can be written to an SSD before running into problems. Most 1TB SSDs these days are rated for around 600–700 TBW, but you can still find other 1TB drives with as low as 220 TBW. The larger the drive, the more the TBW due to the additional number of cells.

Calculate your SSD's remaining life using CrystalDiskInfo

Time to find the TBW rating of your SSD

CrystalDiskInfo is a free utility that shows you detailed information about your storage drives, including drive health (Good, Caution, Bad, etc.), and more importantly, Total Host Writes, which tells you how much data has been written to the SSD till date. Comparing this number to your SSD's TBW rating, you can estimate how many years of flawless operation your SSD has left.

1. Download and install CrystalDiskInfo.
2. Launch it to view the Health Status of your SSD. Find the Total Host Writes field toward the right and note the number you see (in GB).
3. Google the model of your SSD (including the capacity) to find its TBW rating.
4. Divide the Total Host Writes figure by the "TBW x 1000" number to get an idea of how much of your SSD's lifespan you've used up.
5. For instance, the Total Host Writes number for my WD Black SN770 is 31566 GB, and its TBW is 600. Dividing 31566 by 600,000 (600*1000) gives me 0.052, meaning I'm only 5.2% into the SSD's lifespan.

Calculate your SSD's lifespan using failure probability

Using Mean Time Between Failures

Another way you can make an educated guess about the probability of your SSD failing within the warranty period is by using the "MTBF" or Mean Time Between Failures rating. This number is usually over a million hours for most consumer SSDs and can be found on the spec sheet of your SSD on the manufacturer's website. You'll need to do a bit of math before you can arrive at the probable failure rate of your SSD from the MTBF number.

The number of hours indicated by MTBF (1.75 million hours for my SN770) refers to the cumulative hours of operation for a sample size of 1,000 SSDs under regular usage (meaning around 8 hours a day). Hence, taking the example of my SSD, i.e., the WD Black SN770, I need to divide 1.75 million by 8,000 (8 hours per day for 1,000 SSDs) to get 218.75 days. This means that for 1,000 SN770s, one of them will fail every 218.75 days.

This number shows that around 1.66 SSDs (out of 1,000) will fail every year. Dividing 1.66 by 1,000 gives me a 0.16% failure rate for my SN770 within the warranty period. If your SSD has an MTBF of 1 million hours at least, then it has a 0.3% chance of failing within the warranty period, which is pretty slim.