Abstract: A compact gas consumption measuring device which is flexibly insertable into existing gas installations includes in a single compact housing, a permanently installed flowmeter, and a pressure-control device and a shut-off valve, which are modularly constructed in two parts. Additionally, several spatially staggered gas admission and gas discharge ports are provided. To this end, the housing possesses, on the front side, slide-in openings into which one basic module each is inserted and secured. Assigned to each basic module are a function module and a blank module which, depending on the requirement, are insertable into the basic module and are sealable gastight to the outside. The basic modules and the assigned function modules are each provided with a gas intake and gas discharge wells and are connected to each other in such a way that they are connected in series to the flowmeter as well as to the connecting ports for gas admission and for gas exhaust.