18/8 vs 18/10 Stainless Steel: Food Safety Guide

Most people shopping for stainless steel food containers or water bottles have seen these numbers on the box: 18/8, 18/10, sometimes 18/0. They look like they should tell you something important about quality. And they do, partially. But the numbering system hides as much as it reveals, and marketers have learned to use that ambiguity to their advantage.

Here's what those numbers actually mean, what they don't tell you, and how to figure out what you're really buying.

What the Numbers Stand For

The 18/8 and 18/10 designations refer to the percentage of chromium and nickel in the steel alloy.

18/8 means 18% chromium, 8% nickel. The chromium is what makes stainless steel stainless. It forms a passive oxide layer on the surface that resists corrosion. The nickel adds strength, improves formability, and increases corrosion resistance further.

18/10 means 18% chromium, 10% nickel. Same chromium content, 2% more nickel.

18/0 means 18% chromium, zero nickel. You'll find this in some cheaper flatware and magnetic stainless steel. It's ferritic steel (400-series) rather than austenitic (300-series), and it has noticeably less corrosion resistance.

The system originated from the AISI (American Iron and Steel Institute) classification method and maps loosely onto ASTM grade specifications. But "loosely" is the problem.

How 18/8 and 18/10 Map to Grade Numbers

This is where it gets confusing, and where most articles on this topic get it wrong.

18/8 = Grade 304. This is a clean mapping. ASTM A240 specifies Grade 304 as containing 18.0 to 20.0% chromium and 8.0 to 10.5% nickel. An 18/8 alloy falls squarely within this range. Grade 304 is the most common stainless steel in the world. It's the standard for food service equipment, kitchen sinks, brewing tanks, and the vast majority of stainless steel food containers on the market.

18/10 is where it gets messy. An alloy with 18% chromium and 10% nickel could be:

• Grade 304 with higher nickel content. The 304 spec allows up to 10.5% nickel. So an 18/10 alloy can still be 304. Many high-end flatware brands label their products 18/10 when the steel is technically still within the 304 specification.
• Grade 316. This alloy typically contains 16 to 18% chromium, 10 to 14% nickel, and 2 to 3% molybdenum. The nickel content overlaps with 18/10, but the defining feature of 316 is the molybdenum.

The 18/10 label doesn't tell you whether molybdenum is present. And the molybdenum is the ingredient that actually matters most for corrosion resistance and food safety performance.

The Comparison Table

PREN stands for Pitting Resistance Equivalent Number. It's the industry standard formula for predicting a stainless steel's resistance to pitting corrosion: PREN = %Cr + 3.3(%Mo) + 16(%N). The molybdenum multiplier (3.3x) is why even a small amount of Mo has an outsized effect on corrosion resistance.

A 304 alloy with zero molybdenum has a PREN around 18. A 316L alloy with 2.5% molybdenum has a PREN around 25. That's a 39% improvement in pitting resistance from just one added element.

Why Marketers Prefer 18/10 Over Grade Numbers

Walk through the kitchenware aisle of any department store and you'll see "18/10 stainless steel" on most mid-range and high-end flatware boxes. You'll almost never see "Grade 304" or "Grade 316."

There are two reasons.

First, 18/10 sounds better to consumers. The higher number feels like an upgrade. "10" is more than "8," so it must be better, right? Brands know this. The 18/10 label became a shorthand for quality in the flatware industry decades ago, and it stuck.

Second, grade numbers sound industrial. They're harder to market. Nobody puts "ASTM A240 Grade 304" on a gift box. The 18/X system gives brands a quality signal that sounds technical enough to be credible but simple enough for a hang tag.

The problem is that 18/10 has become a marketing term disconnected from its metallurgical meaning. When a brand stamps 18/10 on a product, they're almost always telling you it's 304 with nickel on the higher end of the spec range. They're almost never telling you it's 316.

If a product were actually 316 or 316L, the brand would say so explicitly, because that's a genuine competitive advantage worth advertising. The silence is the signal.

The "18/10 Is Always Better" Misconception

This is the biggest misunderstanding in consumer stainless steel.

Higher nickel content does provide marginal improvements in corrosion resistance and surface finish. But the difference between 8% nickel and 10% nickel is small compared to the difference that molybdenum makes. Going from 304 (no Mo) to 316 (2-3% Mo) is a much bigger jump in performance than going from 18/8 to 18/10 within the 304 family.

Put differently: an 18/8 Grade 316L container with molybdenum will outperform an 18/10 Grade 304 container without it. Every time. In acid resistance, in chloride resistance, in pitting resistance, in long-term durability with tomato sauce, vinegar, citrus, and salt.

The nickel/chromium ratio matters. But if you're choosing a food container based on the 18/X number alone, you're looking at the wrong variable.

What About Nickel Sensitivity and Food Safety?

An estimated 8 to 15% of the population has some degree of nickel sensitivity, with a strong predominance among women, based on contact-allergy epidemiology. For most people, the nickel in stainless steel cookware and containers doesn't cause problems because the passive chromium oxide layer keeps the nickel locked inside the alloy.

But when that layer gets compromised, through acidic foods, salt exposure, or surface damage, nickel can leach.

Kuligowski and Halperin published a study in 1992 in Archives of Environmental Contamination and Toxicology that measured nickel and chromium release from stainless steel cookware. They found that cooking acidic foods (like tomato sauce) in new stainless steel cookware released detectable levels of both nickel and chromium. The levels decreased with subsequent uses as the passive layer stabilized, but the initial release was measurable.

The European Food Safety Authority (EFSA) set the tolerable daily intake (TDI) for nickel at 13 micrograms per kilogram of body weight per day in its 2020 assessment. The FDA's food contact material standards consider 300-series stainless steel safe for food contact, but these standards don't differentiate between 304 and 316 for regulatory purposes.

Here's where grade matters for real-world use: 316L's molybdenum layer provides better resistance to the exact conditions (acid, salt, chloride) that cause nickel leaching. If you're storing tomato soup overnight, packing a citrus-heavy lunch, or using a water bottle for sports drinks with electrolytes, the 316L alloy resists pitting and surface breakdown more effectively than 304.

We covered the detailed science of this in 304 vs 316 stainless steel for food: what's the difference and why it matters.

Does 18/10 help compared to 18/8 for nickel-sensitive people? Counterintuitively, the higher nickel content in 18/10 could theoretically mean more nickel available to leach if the surface is compromised. The better question isn't "how much nickel is in the alloy" but "how well does the alloy's surface layer prevent that nickel from getting out?" And the answer to that question comes down to molybdenum.

How to Tell What You're Actually Getting

The 18/X number on the box isn't enough. Here's how to actually determine the grade of a stainless steel food container or water bottle.

Check for a grade number. If the product or its documentation says "316," "316L," or "surgical-grade stainless steel," you're probably getting 316L. Brands that use this grade will advertise it because it costs more to produce.

Look for what's missing. If the product says "18/10 stainless steel," "food-grade stainless steel," or just "stainless steel" without a grade number, it's almost certainly 304. That's not a bad thing. 304 is the global standard for food service. But it isn't 316.

Check for a magnet test claim. Both 304 and 316 are non-magnetic in their annealed state. A magnet test alone can't tell them apart. If a brand tells you to use a magnet to verify quality, they're really just helping you distinguish austenitic steel (300-series) from ferritic steel (400-series) or non-stainless metals. It doesn't differentiate between 304 and 316.

Ask the manufacturer. Reputable manufacturers can provide a mill certificate or material test report (MTR) that shows the exact alloy composition. If a brand can't tell you the grade, that's your answer.

Most brands don't specify their grade clearly, either. You'll see "food-grade stainless steel" or "premium stainless steel" on packaging without a number. That's almost always 304.

What We Use and Why

We tested six different steel alloys before picking 316L for our food containers and water bottles. The others couldn't handle overnight tomato sauce without pitting.

The 316L designation means two things that matter for daily food contact: molybdenum for corrosion resistance, and the "L" for low carbon (0.03% max versus 0.08% for standard 316). Lower carbon reduces the risk of sensitization, a type of corrosion that happens at grain boundaries when the steel is welded or exposed to sustained heat. For a food container that gets washed in hot water hundreds of times, that's a meaningful difference.

We don't label our products 18/10 because that number would technically apply to our steel but would be misleading. It would put us in the same category as every 304 container on Amazon. The grade is what differentiates the material, not the nickel/chromium shorthand.

For the full comparison between these two grades, including acid test data and corrosion resistance numbers, see our 304 vs 316 stainless steel for food breakdown.

The Bigger Picture on Food Container Materials

The stainless steel numbering system is one piece of a larger problem in food container marketing: vague labels that sound reassuring but don't tell you what you need to know.

"BPA-free" doesn't tell you what replaced the BPA. We covered that in why BPA-free doesn't mean your container is safe. "Food-grade" is a regulatory floor, not a quality ceiling. And "18/10" tells you the nickel content but not the presence (or absence) of the element that actually drives corrosion resistance.

The pattern is the same across materials: the number on the label exists to make you feel confident, not to give you the full picture. The only way to know what you're buying is to look past the marketing shorthand and ask for the actual grade, the actual composition, and the actual test data.

If a company won't share those details, another company will.

Looking for ready-made food-grade stainless steel feeding products? InnoBaby's range is worth a look — use code GADGETDUKE for 15% off.

Disclosure: Affiliate link — we may earn a small commission at no cost to you.

Frequently Asked Questions

Is 18/8 stainless steel food safe?

Yes. 18/8 stainless steel is Grade 304, which the FDA considers safe for food contact. It's the standard for commercial kitchen equipment, food processing, and brewing. For most daily use, including water, dry foods, and short-term food storage, 304 performs well. Where it falls short is in prolonged contact with acidic, salty, or chloride-rich foods, where 316L provides better corrosion resistance.

Is 18/10 better than 18/8 for food containers?

Not necessarily. The extra 2% nickel in 18/10 provides a marginal improvement in corrosion resistance and surface finish. But if both are Grade 304 (which is usually the case), the practical difference in food safety performance is small. A 316L alloy with molybdenum outperforms both, regardless of whether its nickel content is 10% or 12%.

What does the "L" in 316L mean?

The "L" stands for low carbon. Standard 316 allows up to 0.08% carbon, while 316L limits carbon to 0.03%. Lower carbon reduces the risk of intergranular corrosion, a type of corrosion at the grain boundaries that can occur during welding or repeated heating. For food containers that are regularly washed with hot water, the low-carbon variant provides better long-term durability.

Can I tell if my container is 304 or 316 without a lab test?

Not definitively. Both are non-magnetic, look identical, and feel the same. The magnet test only distinguishes austenitic (300-series) from ferritic (400-series) stainless steel. To confirm the grade, check the manufacturer's documentation or request a mill certificate. A handheld XRF analyzer can identify the alloy composition, but most consumers don't have access to one. The most reliable clue: if the brand doesn't say 316 or 316L, it's 304.

Does stainless steel leach nickel into food?

It can, in small amounts, especially during initial uses and when storing acidic foods. Kuligowski and Halperin (1992) measured detectable nickel and chromium release from new stainless steel cookware used with tomato sauce. The release decreased with repeated use as the passive layer stabilized. The FDA considers 300-series stainless steel safe for food contact, and typical leaching levels fall well below the EFSA tolerable daily intake of 13 mcg/kg body weight/day. 316L's molybdenum content provides additional resistance to the conditions that cause leaching.

Why don't more food containers use 316L?

Cost. 316L raw material costs 20 to 30% more than 304 due to the added molybdenum and nickel. Manufacturing processes are the same, but the material cost adds up. For mass-market food containers selling at low price points, the margin on 316L doesn't work. For brands that prioritize material performance over lowest-possible price, 316L is the obvious choice.

Get on the Gadget Duke launch list

We picked 316L for our containers and bottles because the data backs it up, not because the marketing sounded better. Hushknob, our invisible magnetic baby cabinet lock, launches Summer 2026.

Sign up to be notified when new products ship. No spam, no daily newsletter — just a heads-up when something is ready.