Monster Zero Ultra vs Red Bull Sugarfree: 150 vs 80 mg Caffeine

Monster Zero Ultra lists 150 mg of caffeine per 16 fl oz can and Red Bull Sugarfree lists 80 mg per 8.4 fl oz can, which works out to nearly the same caffeine per fluid ounce: about 9.4 mg versus 9.5 mg.

A full can can hold very different totals, though, because the cans differ in size. Per 16 fl oz, the printed figures diverge most on sodium and calories, and the sweetener lists are not identical. Figures come from brand pages, Open Food Facts records and FDA pages listed in the sources.

Key takeaways

• Normalized to ounces, caffeine is nearly identical (about 9.4 mg/oz for Monster Zero Ultra vs about 9.5 mg/oz for Red Bull Sugarfree), but per-can totals differ because the cans differ in size.
• The US 16 fl oz Monster Zero Ultra record on Open Food Facts lists erythritol and sucralose. Red Bull Sugarfree's brand page names sucralose and acesulfame K, so the sweetener systems are not identical.
• Sodium is the clearest label gap: 380 mg per 16 fl oz on the Open Food Facts Monster Zero Ultra record vs 200 mg per 16 fl oz on the Open Food Facts Red Bull Sugarfree record. Check the printed can label, since Open Food Facts is a crowd-sourced database.
• Check the printed can and the size you are buying. Where a detail was not disclosed, this article says so.

At-a-Glance Comparison Table

Factor	Monster Zero Ultra (white can)	Red Bull Sugarfree
Caffeine, per 16 fl oz	150 mg per 16 fl oz (Monster brand page)	About 152 mg, derived from 80 mg per 8.4 fl oz (arithmetic only; no brand-stated 16 fl oz figure)
Caffeine, per 8.4 fl oz	Not stated on brand page (arithmetic: about 79 mg from 150 mg per 16 fl oz)	80 mg per 8.4 fl oz (Red Bull brand page)
Caffeine, per fl oz	About 9.4 mg (150 mg / 16 fl oz, arithmetic)	About 9.5 mg (80 mg / 8.4 fl oz, arithmetic)
Sweeteners	Erythritol and sucralose (16 fl oz Open Food Facts record)	Sucralose and acesulfame K (Red Bull brand page); 16 fl oz Open Food Facts record lists the same two
Calories	10 per 16 fl oz (Monster brand page and 16 fl oz Open Food Facts record)	25 per 16 fl oz (16 fl oz Open Food Facts record); 8.4 fl oz calories not disclosed on brand page
Sugar	0 g per 16 fl oz (16 fl oz Open Food Facts record)	0 g per 16 fl oz (16 fl oz Open Food Facts record)
Carbohydrates	6 g per 16 fl oz (16 fl oz Open Food Facts record)	4 g per 16 fl oz (16 fl oz Open Food Facts record)
Sodium	380 mg per 16 fl oz (16 fl oz Open Food Facts record; check the can label)	200 mg per 16 fl oz (16 fl oz Open Food Facts record); about 105 mg per 8.4 fl oz is arithmetic scaling

Each cell gives the serving size and source. Figures labeled arithmetic are calculations from printed values, not label values for other sizes.

How Much Caffeine Is in Monster Zero Ultra vs Red Bull Sugarfree?

Monster Zero Ultra lists 150 mg of caffeine per 16 fl oz can, and Red Bull Sugarfree lists 80 mg per 8.4 fl oz can. Monster Zero Ultra, the white citrus can, is listed on Monster's brand page in 12, 16, 19.2 and 24 fl oz sizes. The page states 150 mg of caffeine and notes that the caffeine content is based on 16 fl oz. Red Bull Sugarfree's brand page lists 8.4, 12, 16 and 20 fl oz cans, and it states caffeine only for the 8.4 fl oz can, at 80 mg.

Because the two brands state caffeine on different bases, a simple per-can comparison can mislead. Normalizing to ounces brings the concentrations close: 150 mg divided by 16 fl oz is about 9.4 mg per fl oz, and 80 mg divided by 8.4 fl oz is about 9.5 mg per fl oz. These are calculations from the printed figures, not numbers either brand states.

Totals change with the can you buy. Two 16 fl oz Monster Zero Ultra cans add up to 300 mg of caffeine, while five 8.4 fl oz Red Bull Sugarfree cans add up to 400 mg. Because neither brand's page states caffeine for every size it sells, the printed label on the can is the most reliable reference for the size in your hand.

Does Monster Zero Ultra have more caffeine than Red Bull Sugarfree?

Per can, yes: a 16 fl oz Monster Zero Ultra lists 150 mg, while an 8.4 fl oz Red Bull Sugarfree lists 80 mg. Per fluid ounce, though, the two are nearly identical. Comparing a 16 fl oz Monster with an 8.4 fl oz Red Bull mixes two different can sizes, which is why the per-ounce figures give the fairer side-by-side view.

Which has more caffeine per ounce, Monster Ultra or Red Bull?

Per fluid ounce the two are nearly identical: about 9.4 mg for Monster Zero Ultra and about 9.5 mg for Red Bull Sugarfree, calculated from the 16 fl oz and 8.4 fl oz figures. Applying the Red Bull concentration to a 16 fl oz can gives about 152 mg (80 mg / 8.4 fl oz x 16 fl oz). That is an arithmetic result. Red Bull's brand page does not state a 16 fl oz caffeine figure.

The caffeine content of Monster's 12, 19.2 and 24 fl oz cans is not stated on the brand page.

For context, the FDA states that for most adults 400 mg a day is an amount not generally associated with negative effects, which it describes as about two to three 12-fluid-ounce cups of coffee. The FDA also notes wide variation in how sensitive people are to caffeine and how quickly they clear it from the body, so a single daily figure cannot describe every reader.

What Sweeteners Are in Monster Zero Ultra and Red Bull Sugarfree?

The US 16 fl oz Monster Zero Ultra record on Open Food Facts lists erythritol and sucralose. Red Bull Sugarfree's brand page names sucralose and acesulfame K, and its 16 fl oz Open Food Facts record lists sucralose and acesulfame K as well. The systems therefore differ: the Monster record includes erythritol and does not list acesulfame K.

A Canadian 355 mL Monster Zero Ultra record does list acesulfame K. That difference belongs to the Canadian listing and should not be applied to the US 16 fl oz can. Amounts of sucralose, acesulfame K and erythritol in either drink were not disclosed.

Does Red Bull Sugarfree have aspartame?

Red Bull's current brand page names sucralose and acesulfame K as its sweeteners and does not list aspartame. An older Open Food Facts record for the 8.4 fl oz can lists acesulfame K and aspartame, but that record is outdated and does not match the current brand page, so check the can you are holding.

For sweetener context, the FDA says sucralose is about 600 times sweeter than table sugar. The FDA approved sucralose for 15 food categories in 1998 and as a general-purpose sweetener in 1999. The FDA reviewed more than 110 studies on sucralose. The FDA's acceptable daily intake (ADI) for sucralose is 5 mg per kg of body weight per day. Acesulfame potassium is about 200 times sweeter than sugar, was approved for specific categories in 1988 and as a general-purpose sweetener in 2003, and has an FDA ADI of 15 mg per kg of body weight per day.

Erythritol, which appears only in the Monster record, has an FDA letter dated February 20, 2019 (GRN 000789). The FDA said it had no questions about Cargill's conclusion that erythritol is GRAS under its intended conditions of use, and it stated that the letter is not an affirmation that erythritol is GRAS under 21 CFR 170.35.

How Many Calories Are in Monster Zero Ultra?

Monster Zero Ultra lists 10 calories per 16 fl oz can on its brand page, and the 16 fl oz Open Food Facts record also shows 10 kcal and 0 g sugars. The same record lists 6 g of carbohydrates per 16 fl oz can.

Red Bull Sugarfree's 16 fl oz Open Food Facts record lists 25 kcal, 4 g of carbohydrates and 0 g of sugars. Red Bull's brand page text did not include a nutrition panel, and calories for its 8.4 fl oz can were not disclosed there. The printed Nutrition Facts panel on your can is the figure to trust.

Sugar is listed as 0 g on both 16 fl oz records. The two records differ on carbohydrates: 6 g for Monster and 4 g for Red Bull Sugarfree.

Sodium: Printed Figures and Arithmetic Scaling

Sodium shows the widest gap among the figures available. The 16 fl oz Monster Zero Ultra record on Open Food Facts lists 380 mg (0.38 g) of sodium per can, and the 16 fl oz Red Bull Sugarfree record on Open Food Facts lists 200 mg. Neither brand page text disclosed sodium, so both numbers come from Open Food Facts and should be checked against the can's Nutrition Facts panel.

Normalizing to the 8.4 fl oz size makes the comparison clearer. Scaling the 16 fl oz Red Bull record gives about 105 mg (200 / 16 x 8.4), and scaling the Monster record gives about 200 mg (380 / 16 x 8.4). Per fluid ounce, that works out to about 24 mg for Monster and 12.5 mg for Red Bull Sugarfree. These are arithmetic scalings from 16 fl oz records, not label values for 8.4 fl oz cans.

This article does not set a sodium target. The brand pages and label records cited here do not address how these drinks fit into any individual's sodium intake, which depends on diet, health conditions and other foods.

Functional Ingredients on Each Label

Red Bull's own FAQ says Red Bull Zero and Sugarfree contain the same functional ingredients and are made without sugars, using different sweeteners. That FAQ does not compare either product with Monster, so the overlap below comes from each product's own ingredient listing.

• Both lists include caffeine and taurine.
• Red Bull Sugarfree's highlights name B-group vitamins: niacin, pantothenic acid, B6 and B12.
• The Monster record lists niacinamide (vitamin B3), a vitamin B5 source, pyridoxine hydrochloride (B6) and cyanocobalamin (B12).
• Only the Monster record lists Panax ginseng flavor, L-carnitine L-tartrate, sodium citrate, sorbic acid and benzoic acid as preservatives.
• Only the Red Bull record lists sodium bicarbonate, magnesium carbonate, xanthan gum and colors.

The taurine amount in either can was not disclosed. The amount of Panax ginseng flavor or L-carnitine in Monster Zero Ultra was not disclosed, and the specific colors in Red Bull Sugarfree were not disclosed.

How to Read the Caffeine, Sweetener and Sodium Lines

Start with the printed fluid ounce size, then compare figures only at matching sizes. Use this checklist on the can or the Nutrition Facts panel:

• Caffeine: find the mg figure and the serving basis it refers to.
• Sweeteners: match the exact names, such as sucralose, acesulfame potassium or erythritol.
• Sodium: compare mg per listed serving, and note whether the serving is 8.4, 12, 16 or 20 fl oz.
• Calories and carbohydrates: read them from the Nutrition Facts panel, since brand pages may omit them.
• Regional versions: a Canadian can may list ingredients that a US can does not.

The FDA notes that medical experts advise against energy drinks for children and teens because of sugar and caffeine levels, according to the American Academy of Pediatrics, and it advises pregnant or breastfeeding people to talk with a health care provider about limiting caffeine. For policy context, see England Bans Energy Drinks for Under-16s. US Labels Hide Caffeine. For a separate Monster versus Red Bull look at preservatives, see Monster vs Red Bull: Caffeine, Sweeteners and Preservatives.

Aurascan explains each ingredient one by one with cited evidence rather than a single score, which can help you read the lines on the can in your hand.