Pennsylvania sets no legal size limit for a knife you carry. Blade length is not what state law regulates. You can carry a two-inch folding knife or a ten-inch fixed-blade hunting knife, openly or concealed, as long as the knife isn’t a type banned under state law, you aren’t carrying it with criminal intent, and you aren’t in a restricted place like a school or courthouse. The only setting where a specific blade measurement controls is federal property, where pocket knives with blades under 2½ inches get an explicit exemption from the weapons ban.
What Pennsylvania Law Actually Regulates
Nothing in Pennsylvania’s criminal code limits knives by blade length. The two statutes that govern knife carry focus on the type of weapon and the reason you have it. At the state level, the question is never “how long is the blade?” It is “what kind of knife is it, why do you have it, and where are you?”
Prohibited Weapon Types
Pennsylvania’s prohibited offensive weapons statute makes it a first-degree misdemeanor to possess an “offensive weapon,” defined to include bombs, grenades, machine guns, sawed-off shotguns, firearms adapted for concealment or silent discharge, blackjacks, sandbags, metal knuckles, stun guns, tasers, and any other implement for inflicting serious bodily injury that “serves no common lawful purpose.”1Pennsylvania General Assembly. Pennsylvania Code Title 18 Chapter 9 Section 908 – Prohibited Offensive Weapons That last phrase is the hinge. If an item has a common lawful purpose, it falls outside the ban.
Knives almost always clear that bar. A fixed-blade hunting knife, a folding pocket knife, a kitchen knife, even a machete, all have obvious everyday uses. Automatic knives (switchblades) were on the prohibited list until January 2, 2023; they are now legal to own and carry in Pennsylvania.1Pennsylvania General Assembly. Pennsylvania Code Title 18 Chapter 9 Section 908 – Prohibited Offensive Weapons
Carrying With Criminal Intent
A perfectly legal knife becomes a criminal offense if you carry it concealed with the intent to use it in a crime. Under the Possessing Instruments of Crime statute, that conduct is a first-degree misdemeanor. The prosecution must prove both elements: the knife was hidden from view, and you planned to use it criminally.2Pennsylvania General Assembly. Pennsylvania Code Title 18 Chapter 9 Section 907 – Possessing Instruments of Crime
The statute defines “weapon” broadly as anything readily capable of lethal use possessed “under circumstances not manifestly appropriate for lawful uses which it may have.”2Pennsylvania General Assembly. Pennsylvania Code Title 18 Chapter 9 Section 907 – Possessing Instruments of Crime Context carries most of the weight. A folding knife clipped in your pocket on the way to your car after work reads very differently from the same knife tucked in a waistband outside a bar at 2 a.m. Police and prosecutors infer intent from the surrounding circumstances, not from the knife itself.
Outside the instruments-of-crime statute, Pennsylvania draws no distinction between open and concealed carry of a knife. Carrying one in your pocket is treated the same as carrying one on your belt.
The One Place Blade Length Matters: Federal Buildings
Federal facilities follow federal law, not state law. Under 18 U.S.C. § 930, knowingly bringing a dangerous weapon into a federal building is punishable by up to one year in prison, up to five years if you have criminal intent, and up to two years for simple possession in a federal courthouse.3Office of the Law Revision Counsel. 18 U.S. Code 930 – Possession of Firearms and Dangerous Weapons in Federal Facilities
The federal statute explicitly exempts a pocket knife with a blade shorter than 2½ inches from the definition of “dangerous weapon.”3Office of the Law Revision Counsel. 18 U.S. Code 930 – Possession of Firearms and Dangerous Weapons in Federal Facilities A small Swiss Army knife or similar tool clears that threshold and is technically permitted in a federal office building, though individual facilities can impose tighter security screening at their discretion. Anything with a blade of 2½ inches or longer does not get the exemption.
Places You Cannot Carry a Knife of Any Size
K-12 Schools
Possessing any knife on the grounds of, inside the buildings of, or on any vehicle providing transportation to or from a K-12 school is a first-degree misdemeanor. The law covers public, licensed private, and parochial schools, and defines “weapon” extremely broadly to include any knife, cutting instrument, or cutting tool. A small utility knife that is perfectly legal everywhere else can get you arrested on school grounds. The one defense is that the weapon was possessed and used in connection with a lawful supervised school activity or another lawful purpose.4Pennsylvania General Assembly. Pennsylvania Code Title 18 Chapter 9 Section 912 – Possession of Weapon on School Property
State Court Facilities
Knowingly bringing a “dangerous weapon” into a Pennsylvania court facility is a third-degree misdemeanor. The court facility statute uses its own definition, narrower than the school rule but still broad. It specifically lists daggers and automatic knives (those with blades exposed by a switch, push-button, or spring mechanism), plus any other implement for inflicting serious bodily injury that serves no common lawful purpose.5Pennsylvania General Assembly. Pennsylvania Code Title 18 Section 913 – Possession of Weapon in Court Facility
This is a common trap. Automatic knives are legal to carry on the street but specifically banned in courthouses. Daggers are not listed as prohibited weapons under the general statute, but they are named as dangerous weapons in the court facility statute. Leave either in your car before entering a courthouse. Bringing a dangerous weapon into a court facility with intent to use it in a crime raises the charge to a first-degree misdemeanor. Notice must be posted at every public entrance, and you cannot be convicted of simple possession if the required signs were missing and you had no actual knowledge of the restriction.5Pennsylvania General Assembly. Pennsylvania Code Title 18 Section 913 – Possession of Weapon in Court Facility
Post Offices and Airports
U.S. Postal Service property prohibits dangerous or deadly weapons, open or concealed, with no blade-length cutoff.6eCFR. 39 CFR 232.1 – Conduct on Postal Property Leave any knife in your vehicle before you walk inside. At airports, TSA does not permit knives of any kind in carry-on bags. You can pack a knife in checked luggage if it is sheathed or securely wrapped, and the final call on any item rests with the screening officer.7Transportation Security Administration – TSA.gov. Knives
Local Ordinances Can Add Restrictions
Pennsylvania has no statewide preemption law for knives, so cities, boroughs, and townships can impose rules that go beyond state law. A knife that is perfectly legal under state law can still violate a local ordinance depending on where you are standing.
Philadelphia is the clearest example. The city’s municipal code historically prohibited possessing any “cutting weapon” on public streets or public property, defining the term to cover any knife or cutting instrument that can be used as a weapon. The only exceptions were tools being actively used in a trade or profession and Philadelphia Fire Department emergency personnel. The penalty was a minimum fine of $300 and at least 90 days of imprisonment. A federal court approved a settlement in 2023 in which the city conceded the ordinance was unenforceable, so its practical effect is uncertain. Philadelphia separately restricts the sale to minors of double-edged knives, butterfly knives, daggers, and stilettos.
Other Pennsylvania municipalities may have their own rules. If you carry a knife regularly, check the local ordinances for any town where you spend significant time. A call to the local police non-emergency line can save you a charge state law would never impose.
Penalties for a Violation
Where state law is broken, the charge depends on the statute:
- First-degree misdemeanor for possessing a prohibited offensive weapon, carrying any knife concealed with criminal intent, possessing a weapon on school property, or bringing a dangerous weapon into a court facility with criminal intent. A conviction carries a fine of up to $10,000 and up to five years in prison.8Pennsylvania Code. Pennsylvania Code Title 18 Chapter 11 – Authorized Disposition of Offenders
- Third-degree misdemeanor for knowingly bringing a dangerous weapon into a court facility without criminal intent. A conviction carries a fine of up to $2,500 and up to one year in prison.8Pennsylvania Code. Pennsylvania Code Title 18 Chapter 11 – Authorized Disposition of Offenders
Any of these convictions creates a permanent criminal record. Even a third-degree misdemeanor for accidentally carrying a pocket knife into a courthouse can appear on background checks for employment, housing, and professional licensing. The record often outlasts the fine and any jail time.