Colorado Knife Laws: The 3.5-Inch Rule, Automatics Since 2017 and the Denver Exception

The Short Version

Colorado has no permit for knives, no limit on what you can own except the ballistic knife, and no limit on carrying a knife openly. What it has is one definition and one offense. C.R.S. 18-12-101(1)(q) defines a "knife" as "any dagger, dirk, knife, or stiletto with a blade over three and one-half inches in length, or any other dangerous instrument capable of inflicting cutting, stabbing, or tearing wounds," excluding "a hunting or fishing knife carried for sports use." And 18-12-105(1)(a) makes it a class 1 misdemeanor to knowingly and unlawfully carry "a knife concealed on or about his or her person," with exceptions for your home, your business, your own property and your own vehicle while traveling. So a blade of 3.5 inches or under is legal anywhere, open or hidden. A longer blade is legal openly and illegal in a pocket. Automatics, OTFs and gravity knives have been legal statewide since August 9, 2017, under the same rule. The complications are Denver and Boulder, which keep ordinances of their own, and schools, where a knife over 3.5 inches is a felony.

The 3.5-Inch Definition

Everything turns on whether the thing in your pocket is a "knife" under 18-12-101, and the definition has two halves. The first is mechanical: a dagger, dirk, knife or stiletto "with a blade over three and one-half inches in length." Colorado measures the blade from the tip to where it meets the handle, the rule the courts adopted in People v. Pickett in 1977, so the sharpened edge is not the measure. The whole exposed blade is. The second half is the catch-all: "any other dangerous instrument capable of inflicting cutting, stabbing, or tearing wounds." Read alone it would sweep in every pocketknife, screwdriver and box cutter, and the Colorado Supreme Court cut it back in A.P.E. v. People (2001): for a blade of 3.5 inches or less, the prosecution must prove you intended to use the instrument as a weapon, and the knife's design alone does not prove it. A 3-inch folder clipped in a pocket is not a knife under the statute. The same folder carried for a fight is. The hunting and fishing exception is an affirmative defense, which means you raise it and prove it, so it is a defense for a 4-inch fixed blade on the way to a deer stand, not a label to put on a dagger.

What Changed in 2017

Until 2017, 18-12-102 listed the gravity knife and the switchblade knife as "illegal weapons," a class 1 misdemeanor to possess, with the switchblade defined as any knife whose blade opens automatically by a button, spring or other device in the handle. Senate Bill 17-008, effective August 9, 2017, repealed both definitions from 18-12-101 and struck both knives from 18-12-102. Since then an automatic knife, side-opening or out-the-front, and an assisted opener are ordinary knives under state law: legal to buy, own and carry, openly at any length and concealed at 3.5 inches or under, the same as a folder. The ballistic knife, a blade fired from the handle by a spring or charge, was not part of the repeal. It remains on the illegal weapons list with metallic knuckles, the blackjack and the gas gun. Denver did not follow the state. Its municipal code still treats a switchblade or gravity knife as an illegal weapon, which is the subject of section 06.

Concealed, Open and the Exceptions

Colorado's statute is a concealed carry statute and nothing else. It does not say a word about carrying a knife openly, so a 6-inch fixed blade on a belt, a machete on a pack or a sword over a shoulder is legal statewide outside school grounds, however much it alarms people. "Concealed" is not defined in the statute. The jury instruction, adopted in People ex rel. O.R. (2008), is "placed out of sight so as not to be discernible or apparent by ordinary observation." Whether a knife is concealed is a question of fact, which means a jury decides it, and a folder over 3.5 inches riding in a pocket with only the clip showing is exactly the case nobody should want to be the test of. The American Knife and Tool Institute advises against relying on a visible clip, and so do we. The exceptions in 18-12-105(2) are real and generous: no offense in your own dwelling or place of business, on property you own or control, or "in a private automobile or other private means of conveyance" carrying a weapon "for lawful protection of such person's or another's person or property while traveling." A long knife in the glovebox or under the seat is lawful on that exception, and 18-12-105.6 stops any city from writing an ordinance that conflicts with it while you are traveling through.

What You Can Carry, and the One Knife You Cannot Own

At 3.5 inches or under, everything: folders, fixed blades, OTFs, side-opening automatics, assisted openers, butterfly knives, gravity knives, daggers, push daggers, karambits and double-edged blades, open or concealed, with no permit and no registration. Over 3.5 inches, everything on that list openly, and concealed only under the home, business, property, vehicle or hunting-and-fishing exceptions. Nothing in the Revised Statutes names the balisong, the push dagger or the double edge, and nothing restricts buying or selling a knife to an adult. The one knife Colorado bans is the ballistic knife, defined in 18-12-101(1)(b) as "any knife that has a blade that is forcefully projected from the handle by means of a spring-loaded device or explosive charge" and listed in 18-12-102(2) as an illegal weapon with the blackjack, the gas gun and metallic knuckles. Knowingly possessing one is a class 1 misdemeanor under 18-12-102(4). It was a class 5 felony until House Bill 23-1293 moved it in October 2023, and most summaries online still carry the old penalty. Federal law separately bars shipping one across state lines. Metallic knuckles are on the same list, which catches the knuckle-handled trench knife.

Denver, Boulder and Local Rules

Colorado does not preempt local knife law. The only statewide override is 18-12-105.6, which says a local ordinance cannot stop you carrying a weapon in your private vehicle for lawful protection while traveling. Once you step out of the car, the city's rules apply. Denver's are the ones that matter. The Denver Revised Municipal Code, in its dangerous weapons article around section 38-117, still makes it unlawful to carry a knife with a blade over 3.5 inches concealed and still lists switchblade and gravity knives as illegal weapons, with a fine schedule that runs to $999 for a repeat offense. Denver did not amend its code when the state repealed its switchblade ban in 2017, so an OTF that is legal in Aurora is an ordinance violation on the other side of the city line. Boulder keeps a knife ordinance of its own as well. We could not pull either city's code text from here, so treat the Denver summary as what the published secondary sources say and check the current code before you carry an automatic in the city. Outside those two, Colorado's cities generally follow the state rule, but a quick search of a city's municipal code for "knife" before you move there is worth the five minutes.

Where You Cannot Carry

• Schools, colleges and universitiesNo "deadly weapon" that is not a firearm on the grounds or in the buildings of any public or private elementary, middle, junior high, high or vocational school, college, university or seminary: a class 6 felony. For a knife, the courts read that through the 3.5-inch definition, so a blade over 3.5 inches, or any blade you intend as a weapon, is the felony. A 3-inch folder carried as a tool is not, though every school's own code of conduct bans it and will expel a student for it. The weapon may stay unloaded inside a motor vehicle on college grounds, and the home and traveling-vehicle exceptions apply.
  18-12-105.5
• Courthouses and government buildingsNo statewide knife statute, but every Colorado courthouse screens at the door under court security orders and will take any knife, and many city and county buildings post the same rule. Leave it in the car.
  Court orders
• AirportsNo knives past the checkpoint under federal rules. Denver International is also inside Denver, where the city ordinance applies before you reach security.
  TSA
• Private propertyEmployers, venues, bars and property owners set their own policy. Breaking a posted rule gets you removed, and refusing to leave becomes trespass.
  Posted rules

Minors and Felons

Colorado sets no minimum age for owning or carrying a knife and no restriction on selling one to a minor. Its juvenile weapons statutes are written for handguns. A teenager with a knife over 3.5 inches concealed commits the same misdemeanor as an adult, in juvenile court, and schools are where most young people meet the law. For a person with a felony conviction the picture is harsher than in most states. 18-12-108, possession of weapons by previous offenders, covers "a firearm ... or any other weapon that is subject to the provisions of this article 12," and the courts have held since People v. Gross (1992) that a "knife" under 18-12-101 is such a weapon. So a convicted felon who knowingly carries a knife with a blade over 3.5 inches, or any instrument he intends to use as a weapon, commits a class 5 felony, one to three years, whether or not it is concealed. A folder at 3.5 inches or under carried as a tool is outside the statute. The ban lifts for a juvenile adjudication after ten years, and a court can lift it earlier on a showing of good cause.

Penalties

What the Internet Gets Wrong

Five things. First, that switchblades are illegal in Colorado: not since August 9, 2017, except inside Denver. Second, that 3.5 inches is a limit on carrying a knife: it is a limit on concealing one, and open carry has no length rule outside school grounds. Third, that a pocket clip makes a knife open carry: no court has said so, "concealed" is a jury question, and a clip is a bad bet with a 4-inch blade. Fourth, that a ballistic knife is a felony: it was until October 2023, and it is now a class 1 misdemeanor, which several summaries last updated in 2020 still miss, along with the concealed carry charge, which is a class 1 misdemeanor, not class 2, since the 2022 sentencing reform. Fifth, that Colorado has knife preemption: it has it for weapons in your vehicle while traveling and nowhere else, which is why Denver's switchblade ban is still enforceable.

TEKTO Knives for Colorado

Measure the blade. At or under 3.5 inches, the knife is legal everywhere in the state outside Denver, open or in a pocket, automatic or not: the A2 Badger and A5 Spry Mini at 1.85 inches, the A3 Delta Mini at 1.90, the F1 Alpha at 3.10, the F2 Bravo and the X1 Atlas at 3.30, and the F4 Echo at 3.40. The A5 Spry measures 3.50, which is not "over" 3.5, but it is the line itself, and a ruler in a courtroom is the ruler that counts. Carry it openly or in the car if you want no argument. Over the line, the A3 Delta and A7 Zastava at 3.60 and the F3 Charlie and A4 at 3.80 are legal to own and to carry openly, legal in your vehicle, and a misdemeanor in a pocket. Inside Denver, carry the manual folders and leave the automatics at home until the city changes its code.