Short answer: Milwaukee does not sell a standalone M12-to-M18 tool adapter like the generation and system adapters covered in this site’s DeWalt adapters guide. The real bridge between Milwaukee’s M12 and M18 lines is not a separate adapter SKU at all: it is built into the M12 heated jacket line, whose expandable battery pocket accepts both M12 and M18 battery packs. No official Milwaukee-to-non-Milwaukee cross-brand adapter was found in this review, and none is claimed here.
The real M12/M18 bridge: it’s a jacket pocket, not an adapter SKU
Where DeWalt offers discrete adapter products, Milwaukee’s approach is different. The M12 heated jackets include a battery pocket designed to expand for larger batteries. Milwaukee’s current M12 heated jacket product listings state: “The battery holder is hidden in a sleek back pocket that expands for an XC battery… The pocket can be expanded further to fit any M18 battery pack.” This means the garment itself is the bridge: an M18 battery can physically sit in the same pocket and power the jacket, without any separate adapter between the battery and the garment’s connector. That is a design-philosophy difference, not a gap in the product line.
A discontinued adapter that did the reverse: the M18 Power Source
Milwaukee did once sell a related device, though it is no longer available. The M18 Power Source (model 49-24-2371) was, according to Milwaukee’s own product page, “compatible with M12 Heated Jackets with the Expandable Battery Pocket” and “compatible with M18 Compact and XC Batteries,” with a “Powered USB Port [that] Charges Portable Electronic Devices.” Milwaukee’s own product page indicates this item is no longer available for purchase, so it should be treated as discontinued rather than a current buying option.
Chargers that bridge M12 and M18 (without being “adapters”)
Another place the two battery families meet is on the charger. Milwaukee’s M18 & M12 Multi-Voltage Charger (model 48-59-1812) “quickly charges all M12 and M18 Battery Packs” and “accepts all M18 and M12 batteries,” and is marketed specifically for “jobs that require a mix of M12 and M18 Milwaukee cordless power tools.” This is useful cross-family hardware, but it is not a battery adapter. A charger that accepts two battery families is different from a device that lets one battery physically power the other family’s tools.
Turning an M12 battery into a USB power source: the M12 TOP-OFF
Milwaukee also sells the M12 TOP-OFF Power Supply and Charger (model 48-59-1211), which “fits all M12 batteries” and has a “15W Bi-directional USB-C Port to charge phones, tablets, and other personal devices.” It carries a 5-year warranty. Milwaukee also states the M12 TOP-OFF is “compatible with all M12 Heated Gear.” So while this product does not adapt M12 batteries to M18 tools, it does turn an M12 battery into a portable USB power source and is another example of the M12 platform being extended without a tool-battery adapter.
What this guide does not claim
This guide does not claim that any official Milwaukee-to-non-Milwaukee cross-brand adapter exists. None was found in this review. The M18 Power Source is discontinued and is not presented as a current recommendation. This guide also does not speculate about why Milwaukee’s design approach differs from DeWalt’s.
How this was checked
Facts on this page are drawn from Milwaukee’s own M18 Power Source product page, current M12 heated jacket product listings, the M18 & M12 Multi-Voltage Charger product page, and the M12 TOP-OFF Power Supply and Charger product page. The heated-jacket battery-pocket fact could not be confirmed against a directly-fetched Milwaukee page during this review and is sourced at slightly lower confidence than the other facts on this page.
Sources checked: 2026-08-06. A new review date will only be set after the linked pages are re-checked.