King Cobra: Venom, Size, and Behavior Facts

Few snakes command as much fascination—or fear—as the king cobra. It’s the longest venomous snake on Earth, yet its reputation as an aggressive man-eater doesn’t match what field scientists observe.

Average length: 3.18–4 m (10.4–13.1 ft) ·
Maximum recorded length: 5.85 m (19.2 ft) ·
Venom yield per bite: Up to 500 mg ·
LD50 (subcutaneous, mice): 1.2 mg/kg ·
Number of human deaths per year attributed to king cobra: Fewer than 10 globally

Seven key facts, one pattern: the king cobra is exceptional in size but not in venom potency, and its vulnerable status shows a species under pressure.

How venomous is a king cobra?

Toxicity and venom composition

• King cobra venom is primarily neurotoxic, containing neurotoxins that disrupt the nervous system and cardiotoxins that affect the heart (Facts and Details).
• The subcutaneous LD50 in mice is approximately 1.2 mg/kg, which is less potent than many other elapids (PMC review).
• However, the sheer volume delivered per bite—up to 500 mg—makes envenomation potentially fatal without antivenom (Facts and Details).
• The inland taipan (Oxyuranus microlepidotus) holds the title of most venomous snake, with an LD50 of 0.025 mg/kg (Wikipedia).

Comparison with other venomous snakes

Four species, one clear distinction: the king cobra’s venom is less concentrated but delivered in much larger doses.

The implication: the king cobra’s danger comes from venom volume, not concentration.

The implication: judging a snake’s danger by LD50 alone misses the real risk. The king cobra’s bite delivers a payload that can overwhelm even a healthy adult’s system.

Has a king cobra killed a human?

Documented fatalities

• Human deaths from king cobra bites are rare—fewer than 10 per year globally (Facts and Details).
• Most fatalities occur in Asia when the snake is provoked or cornered (PMC review).
• Antivenom exists and is effective if administered promptly (Facts and Details).
• King cobras generally avoid humans and bite only as a last resort (PMC review).

Risk factors and victim profiles

Most king cobra bites happen when people try to capture or kill the snake, or accidentally step on one. Rural farmers and snake handlers are at highest risk (PMC review).

The pattern: the number of king cobra fatalities is eclipsed by deaths from less venomous but more aggressive snakes, such as the saw-scaled viper. The king cobra’s reputation for lethality is largely a product of its size and dramatic display, not its actual aggression.

Is a king cobra bigger than other cobras?

Size comparison with true cobras (Naja)

• The king cobra is the longest venomous snake, reaching up to 5.85 m (19.2 ft) (Wikipedia).
• True cobras (genus Naja) rarely exceed 3 m (10 ft) (Wikipedia).
• Adult king cobras can weigh up to 12 kg (26 lb), heavier than most cobras (Wikipedia).
• The name “Ophiophagus” means “snake-eater,” reflecting its diet of other snakes, including cobras (Facts and Details).

How the king cobra got its name

The king cobra is not a true cobra at all. It belongs to its own genus, Ophiophagus. The “king” refers both to its size and its habit of preying on other snakes.

The trade-off: being the longest venomous snake comes with advantages (reach, intimidation) and disadvantages (slower movement, higher metabolic demands). Its size also makes it a target for habitat loss.

Why is the king cobra not aggressive?

Natural behavior and temperament

• King cobras are shy and avoid confrontation; they prefer to flee (PMC review).
• They raise the front third of their body and hiss as a warning before striking (Facts and Details).
• Aggression is rare unless the snake is protecting its nest or feels trapped (PMC review).
• Field scientists often describe the king cobra as placid unless disturbed or cornered (PMC review).

When do king cobras become defensive?

They may charge and strike from a considerable range if they perceive a threat, but even then, they often give multiple warning displays first.

“The fear of king cobras is largely based on their size and dramatic display, not on actual aggression.”

— Dr. Wolfgang Wüster, herpetologist (Bangor University)

The catch: the very displays that make the king cobra look terrifying—the raised body, the hood, the loud hiss—are actually signals that it wants to avoid a fight. Mistaking the display for aggression leads to many avoidable encounters.

What is the biggest king cobra ever recorded?

Record specimens and verified measurements

• The longest scientifically verified king cobra was 5.85 m (19.2 ft), found in Johor, Malaysia (Wikipedia).
• Reports of 6+ m snakes exist but lack reliable documentation (Wikipedia).
• King cobras continue to grow throughout life; older individuals are larger (PMC review).
• Size varies by region: Southeast Asian specimens tend to be larger than those from India (Facts and Details).

Factors influencing growth

Continuous growth and regional variation mean the true upper size limit is unknown. The 5.85 m record stands, but older individuals in optimal habitats may approach 6 m (PMC review).

“King cobras are specialized snake-eaters; they will even eat other venomous snakes, including cobras.”

— Smithsonian National Zoo curator

The implication: the 5.85 m record stands as the benchmark, but the true upper limit may never be known because large specimens are rarely collected or measured by scientists. What is clear is that the king cobra’s size is an evolutionary strategy to dominate other snakes.

For a deeper dive into the snake’s survival strategies, check out this detailed guide on king cobra venom and behavior.

Frequently asked questions