The K-factor is the number that lets a flow computer turn a stream of electrical pulses into a volume. Pulse-output meters like turbine and positive-displacement meters don't report barrels directly - they emit pulses, and the K-factor says how many pulses make up one unit of volume. This guide explains what a K-factor is, how it is used, why it isn't perfectly constant, and how it differs from the meter factor.
K-Factor in one line: A K-factor is the calibration constant of a pulse-output flow meter, expressed as the number of pulses the meter produces per unit of volume - for example, pulses per barrel or pulses per gallon. A flow computer divides the accumulated pulse count by the K-factor to convert raw pulses into an indicated volume.
Turbine and positive-displacement flow meters produce an electrical pulse train - one pulse each time a fixed increment of fluid passes. A turbine meter emits a pulse per blade passage; a PD meter emits pulses tied to the sweep of its measuring chamber. The raw output is just a count of pulses, which means nothing on its own until you know how much volume each pulse represents. The K-factor supplies exactly that: if a meter's K-factor is 900 pulses per barrel, then 9,000 counted pulses equal 10 barrels.
The flow computer performs this continuously. It counts pulses over a period, divides by the K-factor to get indicated volume, and totalizes. Instantaneous flow rate falls out the same way from the pulse frequency. The K-factor is established by the manufacturer's calibration and is stored in the flow computer's meter configuration.
An ideal meter would have one K-factor across its whole range, but real meters do not. A turbine meter's K-factor varies somewhat with flow rate, especially at low flows where bearing friction and fluid drag disturb the blade speed, and it shifts with fluid viscosity and density. Because of this, high-accuracy applications characterize the meter across its range and use a linearization curve - effectively a K-factor that varies with flow - rather than a single number.
This flow-dependence is one reason proving matters. Proving is done at conditions close to normal operation so the correction (the meter factor) captures the meter's behavior where it actually runs. If flow conditions change substantially, a meter may need re-proving because both its effective K-factor behavior and the correction can shift.
The K-factor and the meter factor work in sequence and should not be conflated. The K-factor turns raw pulses into indicated volume - it is the meter's inherent pulses-per-volume scaling. The meter factor is a separate correction, found by proving, applied to that indicated volume to bring it in line with a certified reference. First pulses become volume via the K-factor; then that volume is fine-tuned via the meter factor.
Both live in the flow computer, and both are values a supervisory system can watch. A cloud SCADA platform such as Merobix reads the configured K-factor and the resulting indicated and corrected volumes from the flow computer over Modbus, OPC UA, or a similar protocol - so measurement staff can confirm the right K-factor is loaded after a meter change and reconcile pulse counts, indicated volume, and net volume remotely without reading the flow computer on site.
A K-factor is the number of pulses a pulse-output meter, such as a turbine or positive-displacement meter, produces per unit of volume - for example pulses per barrel. A flow computer divides the counted pulses by the K-factor to convert the raw pulse output into an indicated volume.
The K-factor converts raw meter pulses into indicated volume (pulses per unit volume). The meter factor is a proving-derived correction applied to that indicated volume to align it with a certified reference. The flow computer applies the K-factor first to get volume, then multiplies by the meter factor to correct it.
Not perfectly. A turbine meter's K-factor drifts with flow rate - particularly at low flow - and with fluid viscosity and density. High-accuracy installations characterize the meter across its range and use a linearization curve instead of a single constant, and they prove the meter near operating conditions to capture its real behavior.
This page references the protocol specifications published by the organizations below. Editions, product capabilities, and documentation change over time - confirm current requirements and specifications directly with the source.
Last reviewed: July 27, 2026. Merobix is not affiliated with, endorsed by, or sponsored by these organizations; their names are used only to identify the standards and products discussed.
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