People can and are charged with and convicted of both burglary and the theft of goods taken during the burglary. Because the two crimes are separate, a person can be convicted of both crimes. Whether a person can be punished for both burglary and theft is a bit more complicated.
For more information on the distinctions between these crimes, see What's the difference between burglary and larceny?, Differences Between Theft, Burglary and Robbery, and Juvenile Theft and Burglary Laws.
Burglary laws were originally enacted to protect people and their possessions inside their homes. Historically, a person committed burglary by entering into a home at night with the intent to commit a felony (a crime punishable by time in state prison) inside. Today, most states have broadened their burglary laws and a person commits burglary by entering into any building without permission with the intent to commit a crime inside. Some burglaries, such as armed burglaries and burglaries of people's homes (also called home invasion burglaries) are often punished more severely than other burglaries. For more information on the crime of burglary, see Burglary: Penalties and Sentencing and Home Invasions.
Intent to commit a crime. In order to be convicted of burglary, the defendant must intend to commit a felony (or sometimes any theft or a felony) inside. In most cases, the circumstances of the entry are such that a jury or judge can conclude that the defendant entered into the building with the intent to commit a crime. For example, if a person forces his way into a closed office in the middle of the night and steals money from the safe, a jury or judge would probably have no trouble concluding he entered the office with the purpose of committing a crime. The actual intended crime does not even need to occur. It is enough to make such an entry with the intent to commit a crime. For example, if a would-be burglar enters a house to commit an assault but is thwarted by the alarm system, the person could still be convicted of burglary.
To commit the crime of theft, also known as larceny, petty theft, or grand theft, a person must take someone else's property without the owner's permission and with the intent to permanently deprive the owner of its use or possession. Theft involves the taking of personal, tangible property. (For example, trying to steal land will not result in theft charges, although other charges may apply.) Items commonly stolen during burglaries include cash, jewelry, home electronics, office equipment, and firearms. For more information on the crime of theft, see Petty Theft & Other Laws.
Because burglary and theft are distinct crimes, a person can be convicted for both. For example, suppose a person breaks into a home intending to steal some jewelry. The defendant takes the jewelry and flees. The defendant can be convicted of both burglary of the house and theft of the jewelry. The burglary was committed as soon as defendant entered the house with criminal intent – before the theft actually occurred. Put another way, the person could be convicted of burglary even if he never managed to take anything; and alternatively, a guest who enters without intending to commit a theft, but who decides after dinner and on the spur of the moment to lift the family silver, could be convicted of theft but not burglary.
It's important not to confuse the question of being convicted of both burglary and theft with another legal issue, that of lesser-included offenses. As just explained, it's legally possible to be convicted of both burglary and theft. But when one crime is a "lesser-included" offense of another crime, two convictions are not legally allowed.
A crime is a lesser–included offense if the crime is composed solely of some, but not all, of the elements of the greater crime, so that it is impossible to commit the greater offense without also committing the lesser. (You can think of the situation as a couple of nesting dolls; the smaller one is necessarily and completely contained in the larger one.) For example, in many states, trespassing (going onto someone else's property without permission) is a lesser-included offense of burglary. If a group of teens goes into a house in order to set the house on fire, they have technically committed both trespassing and burglary, but they cannot be convicted of both. That's because it would be impossible to "go into a person's home without permission intending to commit a crime" (burglary) without also "going onto someone else's property without permission" (trespassing). For more information on trespassing, see Trespassing Penalties.
So, a person can be convicted of both burglary and theft, but oftentimes, a person cannot be punished for both crimes. The states deal with this issue differently. In California, for example, state law prohibits punishing one course of criminal conduct under multiple, different laws. Put another way, if the defendant's actions were geared to accomplishing one objective, he can be convicted for multiple offenses he committed along the way (as long as none of them are lesser-included crimes, as just explained), but he can be punished only for the most severe. (Cal. Pen. Code, § 654.) California judges are required to set ("impose") a sentence for every crime, but must stay (suspend) all but one of the sentences. A person cannot be punished for both burglary and theft if the crimes constitute one course of criminal conduct.
Whether a case presents one criminal objective or multiple criminal objectives depends on the defendant's intent when entering and subsequent acts. (People v. Alford, 180 Cal.App.4th 1463, 1468 (2010).) Under California law, a person cannot be punished for both crimes when the burglary was committed in order to commit theft inside (this is one criminal objective). But suppose a person enters an apartment to steal a gun, takes the weapon, and then realizes that a person is home asleep. The defendant takes advantage of the situation and commits a sexual assault, which was not part of his plan when he entered the home. The defendant could be punished for both the burglary and the assault, because the assault was not a part of the defendant's initial intent or purpose. (The defendant can, of course, be convicted of all three crimes.)
You should always talk to a local criminal defense lawyer if you are accused of or charged with a crime or have questions about the law or the criminal justice process. Even if you believe you have done nothing wrong, speaking to police without first consulting an attorney can seriously damage your case. An attorney can help you understand the laws in your state and present the strongest possible defense.