JBG SMITH Properties ("JBG SMITH") is a real estate investment trust ("REIT") that owns, operates, invests in and develops real estate assets concentrated in leading urban infill submarkets in and around Washington, D.C. We own and operate a portfolio of high-quality commercial and multifamily assets, many of which are amenitized with ancillary retail. In addition, our third-party asset management and real estate services business provides fee-based real estate services to third parties and the legacy funds formerly organized by The JBG Companies ("JBG Legacy Funds"). References to "our share" refer to our ownership percentage of consolidated and unconsolidated assets in real estate ventures.
As of December 31, 2018, our Operating Portfolio consists of 62 operating assets comprising 46 commercial assets totaling approximately 12.9 million square feet (11.3 million square feet at our share) and 16 multifamily assets totaling 6,315 units (4,531 units at our share). Additionally, we have (i) nine assets under construction comprising five commercial assets totaling approximately 1.2 million square feet (927,000 square feet at our share) and four multifamily assets totaling 1,476 units (1,298 units at our share); and (ii) 41 future development assets totaling approximately 23.1 million square feet (19.6 million square feet at our share) of estimated potential development density. We present combined portfolio operating data that aggregates assets that we consolidate in our financial statements and assets in which we own an interest, but do not consolidate in our financial results. For more information regarding our assets, see Item 2 "Properties".
We define "square feet" or "SF" as the amount of rentable square feet of a property that can be rented to tenants, defined as (i) for commercial assets, rentable square footage defined in the current lease and for vacant space the rentable square footage defined in the previous lease for that space, (ii) for multifamily assets, management's estimate of approximate rentable square feet, (iii) for assets under construction and near-term development assets, management's estimate of approximate rentable square feet based on current design plans as of December 31, 2018, or (iv) for future development assets, management's estimate of developable gross square feet based on its current business plans with respect to real estate owned or controlled as of December 31, 2018. "Metro" is the public transportation network serving the Washington, D.C. metropolitan area operated by the Washington Metropolitan Area Transit Authority, and we consider "Metro-served" to be locations, submarkets or assets that are generally nearby and within walking distance of a Metro station, defined as being within 0.5 miles of an existing or planned Metro station.