Santoku Knife Size Guide: Is 18cm (7 Inch) Right for You?

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Updated August 2026 · 9 min read · UK Japanese-steel knife specialists

If you are shopping for a santoku, you will notice something quickly: almost every one you find is 18cm, sold as a 7 inch blade. That is not a coincidence, and it is not laziness on the part of the makers. It is the length that does the most jobs well for the most people.

So the short answer is yes — 18cm is very probably right for you. But "very probably" is not "definitely", and there are real reasons to go a centimetre shorter, or to stop looking at santoku knives altogether and buy a longer gyuto instead. This guide walks through how santoku length is actually measured, why the 18cm size settled where it did, and the three things that should genuinely change your mind: your hands, your board and your storage. You can see the full santoku knife range as you read.

How santoku blade length is actually measured

Blade length is measured along the blade, from the heel — where the edge meets the handle — to the tip. The handle is not included. That is why a "7 inch" santoku is usually around 30cm long in total: roughly 18cm of blade and 12cm of handle and bolster.

The second thing worth knowing is that inch figures are nominal. They describe a size band rather than a precise measurement, and different makers round differently. Our own range shows this clearly: the Riku Damascus VG10 7 inch Santoku has a measured blade length of 168mm and a total length of 300mm. That is 16.8cm, not 17.78cm, and it is still perfectly correctly described as a 7 inch santoku.

None of this matters in the kitchen — the difference between 168mm and 180mm is a fingernail. It matters when you are comparing two products on a screen, or checking whether a blade will clear a knife block slot. If the exact number counts for you, look for the millimetre spec rather than the inch label.

One more measurement that gets ignored and shouldn't: blade height, from edge to spine at the heel. The Riku santoku is 44mm tall and 2.2mm thick at the spine. Height is what gives a santoku its knuckle clearance and its scooping surface, and it is also the dimension that catches people out when they try to slot one into a block built for Western knives.

Why 18cm became the standard santoku size

The santoku design emerged in Japan in the 1940s, as home kitchens there took on more Western ingredients and cooks stopped wanting a separate blade for fish, for meat and for vegetables. The name translates as "three virtues" — usually read as meat, fish and vegetables, sometimes as slicing, dicing and mincing. Either way, the point of the design is that one knife covers the lot.

A knife built to do three jobs has to compromise between them, and length is the main lever. Santoku blades are generally made between about 16cm and 18cm, and the top of that band is where most of them land. Three things push it there:

• Flat edge, push cuts. A santoku has very little belly. You cut by bringing the whole edge straight down onto the board rather than rocking through the food. That means the entire blade length is useful on every cut, so 18cm of santoku gives you more working edge than 18cm of curved chef knife would.
• Board reality. A blade you can move freely on a standard domestic board is a blade you will actually use. At 18cm there is still room either side for your knuckles and for the pile you have already cut.
• Weight ahead of the hand. Past about 18cm a flat-profiled blade starts to feel front-heavy in a pinch grip, and the control that makes a santoku pleasant to use begins to fade.

So 18cm is not a marketing number. It is the point where a flat, tip-light blade is as long as it can usefully be before it stops being nimble. If you want more length than that, the honest answer is that you want a different knife shape, not a longer santoku — which we come back to below.

When a 16–17cm santoku is the better buy

A shorter santoku is not a compromise knife. It is a genuinely different feel — lighter in the hand, quicker to change direction, easier to control for fine work. Our Aiko Black Damascus santoku is 6.7 inch, or 17cm, and it is the one we would point you towards in any of these cases:

• You have smaller hands. Less blade ahead of your pinch grip means less leverage working against you, and the knife feels like an extension of your hand rather than something you are steering.
• Your board is small. If your usual board is around 30 x 20cm or less, a 17cm blade leaves you meaningfully more free board to work on.
• You already own a 20cm chef knife. In that case the santoku is your second knife, not your only one. Buying it a size down gives you two genuinely different tools instead of two knives that overlap.
• You cut a lot of small, fiddly things. Shallots, chillies, ginger, herbs. A shorter blade is simply faster at these.

What you give up is reach. A 17cm santoku will not take a wide cabbage or a big butternut squash in a single pass, and you will notice that on the days you are cooking in volume.

When to size up — and why we'd send you to a gyuto instead

Santoku blades do exist above 18cm, up to around 20cm. We do not stock one, and that is deliberate.

Once you go past 18cm, the qualities that make a santoku worth owning start to work against it. The flat profile that gives such clean push cuts becomes harder to keep in full contact with the board over a longer edge. The blunt sheepsfoot tip, which is a non-issue at 18cm, becomes a real limitation when you are working a longer knife into a joint or trimming something awkward. And the extra weight sits out at the front, where you feel it most.

A 20cm gyuto — the Japanese take on the Western chef knife — solves all three. Its curved belly is designed for the rocking motion that suits a longer blade, and its pointed tip does the detail work the santoku cannot. Our Haruta 8 inch VG10 Gyuto is £89.99, exactly the same price as the 7 inch Haruta santoku, so this is a choice about shape rather than budget.

Size up to a gyuto if you regularly break down whole chickens or large joints, cook for six or more, work on a large board, or find yourself wanting a fine point. Stay with an 18cm santoku if most of your prep is vegetables, fish and boneless meat on a normal domestic board. If you are torn, our santoku vs gyuto comparison goes through the shapes in more depth, and the guide to first chef knife sizes covers the gyuto side of the decision.

Hands, boards and storage: the three fit checks

Your hand and your grip

Length matters less here than balance. A santoku should feel neutral or very slightly blade-forward when you hold it in a pinch grip — thumb and forefinger on the blade just ahead of the handle. If the knife wants to nose down under its own weight, it is too much blade for your hand.

Handle shape does a lot of this work. The Haruta santoku uses a rounded oval wooden handle, the Riku a moulded G-10 Garolite handle, and the Aiko a stabilised burl wood and resin handle — all different in the hand at the same blade length. If you are between sizes, choosing on handle comfort is a better guide than choosing on the centimetre.

Your chopping board

As a working rule of thumb, you want a clear cutting area longer than the blade, plus room either side for your knuckles and for what you have already cut. An 18cm santoku is comfortable on a board of roughly 40 x 30cm and workable on 30 x 20cm. Below that you will spend more time shuffling piles than cutting.

Board material matters too, and it matters more with harder Japanese-steel blades than with soft European ones. Wood and end-grain boards are kind to an edge; glass, stone, ceramic and steel will chip one. If you are buying a new santoku and still cutting on glass, replace the board first — it will make more difference to your edge than any upgrade in steel.

Storage

This is where blade height catches people out. A santoku is tall — 44mm at the heel on our Riku — and plenty of knife blocks are cut with narrow slots designed for slim Western blades. Measure the slot before you assume a santoku will drop in.

Two alternatives avoid the problem. A magnetic wooden wall rack takes any blade shape and comes in 30cm, 40cm, 45cm and 61cm lengths, so you size it to the number of knives rather than to their profile. Or a wooden drawer organiser, which holds up to seven knives flat and keeps the edges off each other. Several of our santoku options also ship with their own solution — the Haruta comes with a fitted wooden scabbard.

Santoku vs gyuto vs nakiri: length compared

Length only means something in the context of blade shape. Here is how the three overlap in our own range.

Knife	Blade length in our range	Edge profile	Best at
Santoku	17–18cm (6.7–7 in)	Mostly flat, sheepsfoot tip	All-round prep on a normal board
Nakiri	17–19.5cm (6.7–7.7 in)	Dead flat, squared-off end	Vegetables in volume, straight-down cuts
Gyuto / chef	20–23.5cm (8–9.3 in)	Curved belly, pointed tip	Rocking, larger proteins, long slices

The useful pattern: santoku and nakiri live in the same length band but do different jobs, while the gyuto is a size class up. If vegetables dominate your cooking, the length question becomes a shape question — our santoku vs nakiri comparison settles that one.

Three santoku knives, three sizes

All three of these are Japanese-steel blades with the same basic job description. They differ in length, in feel and in what you get for the money.

Our santoku range compared, by size

Santoku	Nominal blade	Steel & handle	Price	Best for
Aiko Black 6.7″ Santoku	17cm (6.7 in)	VG10, 67 layers · burl wood & resin	£79.99	Smaller hands, small boards
Riku 7″ Santoku — best value	168mm measured	VG10, 67 layers · G-10 Garolite	£79.99	Full specs, hard-wearing handle
Minato 7″ Santoku	18cm (7 in)	AUS-10, 60±2 HRC · rosewood	£79.99	A published hardness figure
Haruta 7″ Santoku	18cm (7 in)	VG10, 67 layers · oval wood + scabbard	£89.99	The default all-rounder
Chikashi 7″ Santoku	18cm (7 in)	VG10, 67 layers · abalone	£96.99	Finest edge angle, showpiece handle

Worth noticing: price barely moves with length. Across the range it is the steel, the finish and the handle material that set the price, not the extra centimetre. If you were hoping a shorter santoku would be cheaper, it generally won't be.

Five sizing mistakes worth avoiding

1. Buying by the inch label alone. Two knives sold as 7 inch can differ by a centimetre. If the number matters, check the millimetre spec.
2. Ignoring blade height. Length gets all the attention, but height determines knuckle clearance and whether the knife fits your block. A 44mm santoku will not go into a slot cut for a 30mm carving knife.
3. Sizing up to replace a chef knife. A longer santoku is not a shorter gyuto. If you want the reach and the tip, buy the gyuto.
4. Matching the santoku to a knife you already own. Buying an 18cm santoku when you already have a 20cm chef knife gives you two knives that fight for the same jobs. Go 17cm and get genuine range instead.
5. Forgetting the board. The best-sized knife in the world is uncomfortable on a 25cm board. Sort the board first; it is the cheaper fix.

Care and sharpening at 18cm

Blade length changes very little about maintenance. It does not change the sharpening angle, and it does not change how often you need to sharpen. What it changes is the stroke count: a longer blade means more passes to cover the whole edge, worked in overlapping sections.

Japanese-steel knives are typically finished at a narrower angle than European ones, which is a large part of why they feel so sharp. You can see it in our own specs — the Minato santoku carries a 15° mirror-polished edge, and the Chikashi is ground at 8–12° per side. Match whatever angle your knife came with rather than reaching for a generic 20°; our guide to the correct Japanese knife sharpening angle explains how to find and hold it.

A standard 180–200mm whetstone handles an 18cm santoku without any special technique. Our two-stone 400/1000 and 3000/8000 set is £59.99 and covers everything from repairing a chipped edge to a final polish, and the step-by-step whetstone guide walks through the motion.

The rest is the usual list, and it applies at any length: hand wash and dry immediately, never the dishwasher, no bones or frozen food, and keep the edge off other metal in the drawer.

Santoku size FAQ

Is 18cm the standard size for a santoku knife?

Broadly yes. Santoku blades are usually made between about 16cm and 18cm, and 18cm — listed as 7 inch — is the size you will see most often in the UK. Every santoku in our range is either 17cm or 18cm, because that band suits the widest spread of hands, boards and everyday jobs.

Is a santoku the same as a 7 inch chef knife?

No. They share a length band but not a shape. A santoku has a flat edge and a sheepsfoot tip that curves down to meet it, so it is built for straight push cuts. A chef knife or gyuto has a curved belly and a pointed tip, so it rocks. At the same length the santoku gives you more usable flat edge; the chef knife gives you more tip work.

What does 7 inch actually measure on a santoku?

It measures the blade, from the heel to the tip, with the handle excluded. It is also a nominal figure rather than a precise one. Our Riku 7 inch Santoku, for example, has a measured blade length of 168mm and a total length of 300mm. Treat any inch figure as a size band, and check the millimetre spec if the exact number matters.

Should I buy a 16cm or an 18cm santoku?

Buy 18cm unless you have a specific reason not to. The extra centimetre or two costs you nothing in control and gives you noticeably more room when you are slicing a cabbage or a large squash. Go shorter if you have small hands, a small board, or you already own a longer chef knife and want the santoku for detail work.

Can an 18cm santoku replace a chef knife?

For most home cooking, yes. It handles vegetables, fish and boneless meat comfortably. Where it runs short is anything tall or long — a whole melon, a large joint, a big loaf — and anything that wants a fine point. If you cook a lot of those, keep a 20cm gyuto alongside it rather than sizing the santoku up.

What size santoku is best for smaller hands?

A 17cm blade is the easier starting point, because the shorter blade puts less weight ahead of your grip and feels more controllable in a pinch grip. Handle shape matters at least as much as length, though: a slimmer oval or octagonal handle usually suits a smaller hand better than a thick, deep one.

Will an 18cm santoku fit a standard knife block?

Usually, but measure first. Blocks are often cut for Western blades, which are narrower from edge to spine than a santoku. Our Riku santoku is 44mm tall at the heel, and a slot cut for a slim carving knife will not take that. A magnetic rack or a drawer organiser avoids the problem entirely.

Do longer santoku knives cost more?

Not meaningfully, in this size band. Across our range the price is set by steel, finish and handle rather than by the extra centimetre. The 6.7 inch Aiko santoku, the 7 inch Riku santoku and the 7 inch Minato santoku are all £79.99; the 7 inch Haruta is £89.99 and the 7 inch Chikashi is £96.99.

Santoku or nakiri, if I mostly cut vegetables?

A nakiri, at a similar length, is the more specialised vegetable knife: a taller, dead flat blade with a squared-off end, so the whole edge lands on the board at once. A santoku gives up a little of that in exchange for handling fish and meat as well. If vegetables are 90 percent of your prep, the nakiri wins; if not, the santoku is the more useful single knife.

Can I sharpen an 18cm santoku on a normal whetstone?

Yes. A standard 180mm to 200mm stone takes an 18cm blade without any special technique, and the length makes no difference to the angle you hold. Work in sections, keep the angle consistent, and finish on a fine grit. Our two-stone 400/1000 and 3000/8000 set covers repair through to polishing.

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