In brief
If you have eaten wagyu outside Japan, you have almost certainly been told two things: that A5 is the highest grade, and that only a tiny fraction of Japanese cattle achieve it.
The first is true. The second is not, and it has not been true for a long time.
What follows is how Japan’s beef grading system actually works, taken from the official regulation and the government’s own published statistics. This is not an argument that A5 is bad. It isn’t. It is an argument that a single letter and a single number cannot carry the weight the English-speaking market currently puts on them.
Japan’s beef carcass grading is administered by the Japan Meat Grading Association. The letter — A, B or C — is the yield grade. It is not a judgment call. It is arithmetic:
Yield base value = 67.37
+ 0.130 × rib eye area (cm²)
+ 0.667 × rib thickness (cm)
− 0.025 × cold carcass weight (kg)
− 0.896 × subcutaneous fat thickness (cm)
(+2.049 for beef breeds)A = 72 or above / B = 69 to 72 / C = below 69
Four variables: an area, two thicknesses and a weight. There is no term in this equation for flavour, aroma, texture or fat quality.
The yield grade exists to tell a producer and a wholesaler how much saleable meat they will get from a carcass. It is an economic measure and was never designed to be anything else. When a menu says A5, the “A” is describing the shape of an animal you will never see.
The quality grade, 1 to 5, is assessed on four items: beef marbling (BMS), beef colour and brightness, firmness and texture, and fat colour, lustre and quality. The final grade is the lowest of the four.
But only one of them has a published numeric scale. Marbling runs on a 12-point BMS scale, and grade 5 requires BMS No. 8 or above. The other three are graded on relative descriptions — very good, good, average — and in practice most carcasses sit near the top of them.
The result is that the quality grade functions as a marbling score.
You can see this in the numbers. In May 2026, 98.4% of steer wagyu carcasses received an A for yield. 76.6% received a 5 for quality. Yield no longer separates anything. Marbling does all the work.
This is the part most English-language sources get wrong, and not by a little.
| Year | A5 share of steer wagyu |
|---|---|
| 2001 | 11.8% |
| 2018 | 40.5% |
| 2022 | 59.7% |
| May 2026 | 76.6% |
Across all wagyu, steers and heifers together, the figure is 68.2%. Three out of four steer wagyu carcasses are now A5. Twenty-five years ago it was roughly one in eight.
This is not because grading became lenient. The BMS 8 threshold has not moved, and Japan’s Ministry of Agriculture states plainly that breeding and feeding genuinely improved. But the consequence is the same either way:
A5 has not become worse. It has stopped being a filter.
If 76% of a population shares a label, that label cannot help you choose within the population. It tells you the animal cleared a bar that almost everything now clears.
The market has already noticed. The price gap between A5 and A4 carcasses has narrowed to roughly 6.5%, and in January 2026 A5 hit an eleven-year low.
Here is a figure published by Japan’s Ministry of Agriculture, Forestry and Fisheries. Two carcasses, both graded BMS No. 9. Measured intramuscular fat content: 35.3% and 64.6%.
Same label. Nearly double the fat.
The ministry’s own commentary notes that fine marbling — kozashi — can lower actual fat content without lowering the BMS number. The grading system cannot distinguish between two very different eating experiences that happen to look similar at the cut surface.
Research into what actually makes wagyu taste the way it does points consistently at fat composition and aroma.
None of this is measured. Oleic acid content is not graded. Melting point is not graded. Aroma is not graded.
None of this is a fringe opinion. The Ministry of Agriculture writes, in an official policy document, that in order to align beef production with consumer needs it is important to focus on traits other than marbling — feed efficiency, fertility, fat quality and fine marbling.
Concrete steps are already in place.
There is a cost to optimising an entire industry around one number.
Because marbling drives price, breeding has concentrated on a small number of sires. The inbreeding coefficient of registered female Japanese Black cattle rose from 4.8% for animals born in 1986 to 9.7% for those born in 2020. The offspring of just 15 sires account for roughly half of the cattle traded at market. The Ministry lists the risks explicitly: stillbirth, infertility, lower conception rates, poor growth.
Hyogo Prefecture, home of Tajima cattle, has gone as far as capping the annual number of semen straws distributed per sire.
A single measuring stick has been narrowing the genetic base of wagyu itself. Moving beyond A5 is not a matter of taste preference. It is a condition for wagyu continuing to exist in the form we know.
That is Part 2, and it is the harder question. If the grade cannot tell you which wagyu is worth your money, something else has to.
The short version: bloodline, the quality of the fat rather than the quantity, and how long the animal was actually fed. Two of those three can be verified by anyone, because Japan runs a national cattle traceability system and every restaurant serving yakiniku, sukiyaki, shabu-shabu or steak is legally required to display the individual identification number of the animal on the plate.
We are writing that piece now.
Every figure on this page comes from a primary Japanese source.