Every 3D printer has a build envelope. The build envelope is the maximum area the printer can print and determines how large of an object the printer can build. The build envelope is determined by the size of the build plate and the range of the extruder along the X, Y and Z axes.
The size of the build envelope is indicated with 3 numbers—the length, width and height. It can also be indicated by 1 number in cubic inches or centimeters.
Here are some examples of build envelope dimensions for some popular desktop 3D printers:
MakerBotReplicator2 - 410 cubic inches or 12.2 L x 6.1 W x 6 H inches.
Cube, byCubify- 5.5 x 5.5 x 5.5 inches.
AfiniaH Series - 5 x 5 x 5 inches.
Generally speaking, the larger the build envelope the better when it comes to 3D printing. Some commercial-grade printers have large build envelopes and can build fairly large objects. The Objet 1000 has a build envelope of 39.3 L x 31.4 W x 19.6 H inches.
The build envelope is an important spec to consider when comparing 3D printers.