The AS SSD Score Formula: How the Total Is Calculated
Every AS SSD Benchmark run ends with three numbers: a read score, a write score and a total. They look official enough that people quote them as if they were measured — but they are calculated, from the four test rows above them, using a formula the author made public. This page sets out the simplified formula exactly as secondary guides document it, explains why it is weighted the way it is, and covers the two comparison mistakes the formula makes dangerous. You can run the test yourself from our download page.
The simplified formula
Secondary guides that document the author’s published formula give it in this simplified form (see sources below):
Read score = Seq Read × 0.1 + 4K Read + 4K-64Thrd Read
Write score = Seq Write × 0.1 + 4K Write + 4K-64Thrd Write
The total score is a combination of the read and write scores. Treat this as what it is labelled: a simplified form of the calculation, as reported by secondary guides such as PC Hardware Pro’s AS SSD walkthrough and MundoBytes, both of which describe the same structure — sequential speed weighted at a tenth, the two 4K results added at full weight. We deliberately do not print a more elaborate version of the formula: more complex variants circulate online without a verifiable source, and a scoring formula you cannot trace is worse than a simplified one you can.
Why sequential speed counts for almost nothing
The 0.1 multiplier is the most important design decision in the formula. A drive that reads sequentially at 3,000 MB/s contributes only 300 points from that row, while its 4K and 4K-64Thrd rows contribute their full MB/s values — and on a fast drive the 4K-64Thrd row alone can be worth well over a thousand points. In other words, the total score is mostly a random-performance score. That is a deliberate editorial choice by the tool’s author: small-block random access is what an operating system does all day, so a benchmark score meant to rank drives by how responsive they feel should reward 4K behaviour and treat sequential bragging rights as a minor input. It also explains a pattern that confuses many first-time users — a drive with modest sequential numbers but strong 4K results can outscore a drive with spectacular sequential numbers and ordinary 4K results. We show a real example of exactly that in Sequential vs 4K scores.
A worked sanity check
You can use the simplified formula to sanity-check any published result. Take the Intel SSD 660p 1 TB as reviewed by Legit Reviews (AS SSD 2.0.6485.19676): sequential speeds of 1,747.2 MB/s read and 1,681.9 MB/s write, and 4K results of 54 MB/s read and 136 MB/s write, with a published total of 2,433 points. The sequential rows contribute roughly 175 points on the read side and 168 on the write side under the simplified formula — a small fraction of the total. The rest has to come from the 4K and 4K-64Thrd rows, which is precisely the weighting the formula describes. If a screenshot you find online shows a total that cannot be reconciled with its own rows at all, treat the screenshot — not the formula — with suspicion.
Why totals cannot be compared across versions
The results archive on this site spans AS SSD 1.7, 1.8 and 2.0, because that is what review sites used at the time — Legit Reviews, for example, tested the Samsung SM951 with version 1.7.4739.38088 and the Phison E12 reference drive with version 2.0.6485.19676. Test internals changed between those generations, so a total from a 1.7 run and a total from a 2.0 run are not points on one scale. Comparing them as if they were is the single most common scoring error on forums. When you line results up side by side — as we do in AS SSD scores compared — note the version printed with each result and only draw conclusions within the same version.
Why test size matters too
AS SSD lets you choose a test file of 1, 3, 5 or 10 GB; the default is 1 GB. The choice changes what the rows measure. A 1 GB run fits comfortably inside the fast cache area of many drives, while a 10 GB run pushes well past it and exposes sustained-write behaviour that the short test never touches. Two totals produced with different test sizes are therefore answers to different questions, even on the same drive, in the same version, on the same day. When you publish or compare a score, state the test size next to it — and if a comparison does not state one, assume the 1 GB default but do not build conclusions on the assumption.
What the formula does not include
Two parts of the tool never enter the score at all. The Copy-Benchmark (ISO, Program and Game scenarios) reports its own speeds and times, but contributes nothing to the read, write or total score. The Compression-Benchmark draws a graph of performance against data compressibility — vital for understanding controllers that accelerate compressible data — but likewise adds no points; we explain that graph in Compression-Benchmark explained. Access time is displayed in the grid but is not an input to the simplified formula either; it is diagnostic information, covered separately in access time explained. Finally, remember what the score is: a compact summary of one short synthetic workload, on one system, on one day. Used that way — and compared like-for-like, as our guide to judging a score recommends — it is a genuinely useful number. Used as a universal ranking across versions, test sizes and systems, it is numerology.
Sources: simplified formula as documented by PC Hardware Pro and MundoBytes; review results from Legit Reviews as linked above.