---
term: "Melt Volume Rate"
category: "mfi-testing"
shortDefinition: "MVR is the volumetric flow rate of molten polymer through the standard MFI die, reported in cm³/10 min; relates to MFR through melt density at test temperature."
formula: "MVR = MFR / ρm"
url: "https://vectorbtc.com.tr/resources/glossary/melt-volume-rate/"
---

**Melt volume rate (MVR)** expresses the same extrusion experiment as MFR but in **volumetric** rather than mass units. It is advantageous when comparing materials of **different densities** at process temperature—such as filled versus unfilled grades—because volumetric throughput often correlates more directly with **screw recovery** in injection molding.

**MVR** is measured using **piston displacement** and timed cuts, with melt density either measured or taken from tabulated values for the resin family. Small errors in temperature or pressure head propagate to MVR uncertainty; machines require regular verification of **die dimensions and temperature uniformity**.

Conversion between **MFR and MVR** demands accurate **melt density ρm**, which itself varies with temperature, pressure, and molecular architecture. Using room-temperature solid density instead of melt density introduces systematic bias.

Processors may specify MVR limits alongside MFR in material datasheets for **high-cavitation molds** where volumetric shot control dominates short-shot defects.