Flow - Mass Converter

Mass flow rate measures how much mass of a substance passes a given point per unit of time — unlike volumetric flow rate, it does not change with temperature or pressure, since mass is conserved regardless of how much a fluid expands or contracts. This makes mass flow the preferred quantity for accurate material balances, custody transfer (billing for material actually delivered), and any process where the fluid's density might vary.

Our Flow - Mass converter supports units across the full metric scale. The core units — kilogram/second (the SI-consistent base), gram/second, gram/minute, gram/hour, and gram/day, along with their milligram equivalents — cover laboratory and small-scale process measurements. The complete metric prefix ladder is also included, from exagram/second and petagram/second down to microgram/second, so extremely large industrial flows and extremely small trace flows can both be expressed precisely without awkward exponents.

For bulk industrial use, the converter includes metric ton per second, minute, hour, and day — standard in mining, bulk materials handling, and large-scale chemical processing — as well as the US short ton per hour. Imperial units round out the list with pound per second, minute, and hour, commonly seen in US engineering specifications and process design documents.

To convert, choose your starting and target units from the dropdown lists and enter a value — the result appears instantly, calculated to up to 12 significant digits. For example, converting 1 metric ton per hour to kilograms per second gives about 0.278 kg/s, a conversion frequently needed when comparing a bulk-handling specification to a process engineering calculation.

Mass flow rate conversions matter across chemical process engineering (mass balances around reactors, columns, and heat exchangers), power generation (steam and fuel mass flow into boilers and turbines), aerospace propulsion (propellant mass flow rate in jet and rocket engines, which directly determines thrust), and bulk material handling (conveyor and hopper throughput typically rated in tons per hour). Because mass flow doesn't depend on the fluid's changing density, it's also the standard for custody-transfer metering in industries like natural gas and petrochemicals, where buyer and seller must agree on exactly how much material changed hands.

Mass flow rate also relates directly to the Flow (volumetric) converter elsewhere on this site — multiply a mass flow rate by specific volume, or divide it by density, and you get the equivalent volumetric flow rate. Keeping a precise, correctly-converted mass flow figure on hand makes that follow-on calculation reliable rather than a source of unit-mismatch errors when a process specification mixes mass-based and volume-based flow figures.

All conversion factors used in this tool are drawn from precise, standard definitions of mass and time units, so results are reliable for process calculations, equipment specifications, and technical documentation. The converter is free, requires no account, and works equally well on desktop and mobile devices.