diff --git a/src/NETCDF/dump_netcdf.cpp b/src/NETCDF/dump_netcdf.cpp
index 8f5d6f9efd..f67bf8c2ff 100644
--- a/src/NETCDF/dump_netcdf.cpp
+++ b/src/NETCDF/dump_netcdf.cpp
@@ -19,6 +19,7 @@
 #if defined(LMP_HAS_NETCDF)
 
 #include "dump_netcdf.h"
+#include "netcdf_units.h"
 
 #include "atom.h"
 #include "comm.h"
@@ -101,7 +102,7 @@ DumpNetCDF::DumpNetCDF(LAMMPS *lmp, int narg, char **arg) :
     int idim = 0;
     int ndims = 1;
     std::string mangled = earg[i];
-    Quantity quantity = Quantity::Unknown;
+    Quantity quantity = Quantity::UNKNOWN;
     bool constant = false;
 
     // name mangling
@@ -110,12 +111,12 @@ DumpNetCDF::DumpNetCDF(LAMMPS *lmp, int narg, char **arg) :
       idim = mangled[0] - 'x';
       ndims = 3;
       mangled = "coordinates";
-      quantity = Quantity::Distance;
+      quantity = Quantity::DISTANCE;
     } else if ((mangled == "vx") || (mangled == "vy") || (mangled == "vz")) {
       idim = mangled[1] - 'x';
       ndims = 3;
       mangled = "velocities";
-      quantity = Quantity::Velocity;
+      quantity = Quantity::VELOCITY;
     } else if ((mangled == "xs") || (mangled == "ys") || (mangled == "zs")) {
       idim = mangled[0] - 'x';
       ndims = 3;
@@ -125,17 +126,17 @@ DumpNetCDF::DumpNetCDF(LAMMPS *lmp, int narg, char **arg) :
       idim = mangled[0] - 'x';
       ndims = 3;
       mangled = "unwrapped_coordinates";
-      quantity = Quantity::Distance;
+      quantity = Quantity::DISTANCE;
     } else if ((mangled == "fx") || (mangled == "fy") || (mangled == "fz")) {
       idim = mangled[1] - 'x';
       ndims = 3;
       mangled = "forces";
-      quantity = Quantity::Force;
+      quantity = Quantity::FORCE;
     } else if ((mangled == "mux") || (mangled == "muy") || (mangled == "muz")) {
       idim = mangled[2] - 'x';
       ndims = 3;
       mangled = "mu";
-      quantity = Quantity::DipoleMoment;
+      quantity = Quantity::DIPOLE_MOMENT;
     } else if (utils::strmatch(mangled, "^c_")) {
       std::size_t found = mangled.find('[');
       if (found != std::string::npos) {
@@ -434,7 +435,7 @@ void DumpNetCDF::openfile()
           }
         }
 
-        std::string unit = this->unit_of(perat[i].quantity);
+        std::string unit = get_unit_for(update->unit_style, perat[i].quantity, error);
         if (!unit.empty()) {
           NCERR( nc_put_att_text(ncid, perat[i].var, NC_UNITS_STR, unit.size(), unit.c_str()) );
         }
@@ -470,10 +471,10 @@ void DumpNetCDF::openfile()
       NCERR( nc_put_att_text(ncid, NC_GLOBAL, "programVersion",strlen(lmp->version), lmp->version) );
 
       // units & scale
-      std::string unit = this->unit_of(Quantity::Time);
+      std::string unit = get_unit_for(update->unit_style, Quantity::TIME, error);
       NCERR( nc_put_att_text(ncid, time_var, NC_UNITS_STR, unit.size(), unit.c_str()) );
 
-      unit = this->unit_of(Quantity::Distance);
+      unit = get_unit_for(update->unit_style, Quantity::DISTANCE, error);
       NCERR( nc_put_att_text(ncid, cell_origin_var, NC_UNITS_STR, unit.size(), unit.c_str()) );
       NCERR( nc_put_att_text(ncid, cell_lengths_var, NC_UNITS_STR, unit.size(), unit.c_str()) );
 
@@ -892,94 +893,4 @@ void DumpNetCDF::ncerr(int err, const char *descr, int line)
   }
 }
 
-/* ---------------------------------------------------------------------- */
-
-std::string DumpNetCDF::unit_of(Quantity quantity) {
-  if (!strcmp(update->unit_style, "lj")) {
-    if (quantity == Quantity::Unknown) {
-      return "";
-    } else {
-      return "lj";
-    }
-  } else if (!strcmp(update->unit_style, "real")) {
-    switch (quantity) {
-    case Quantity::Unknown:
-      return "";
-    case Quantity::Time:
-      return "femtosecond";
-    case Quantity::Distance:
-      return "Angstrom";
-    case Quantity::Velocity:
-      return "Angstrom/femtosecond";
-    case Quantity::Force:
-      return "(Kcal/mol)/Angstrom)";
-    case Quantity::DipoleMoment:
-      return "e * Angstrom";
-    }
-  } else if (!strcmp(update->unit_style, "metal")) {
-    switch (quantity) {
-    case Quantity::Unknown:
-      return "";
-    case Quantity::Time:
-      return "picosecond";
-    case Quantity::Distance:
-      return "Angstrom";
-    case Quantity::Velocity:
-      return "Angstrom/picosecond";
-    case Quantity::Force:
-      return "eV/Angstrom";
-    case Quantity::DipoleMoment:
-      return "e * Angstrom";
-    }
-  } else if (!strcmp(update->unit_style, "si")) {
-    switch (quantity) {
-    case Quantity::Unknown:
-      return "";
-    case Quantity::Time:
-      return "second";
-    case Quantity::Distance:
-      return "meter";
-    case Quantity::Velocity:
-      return "meter/second";
-    case Quantity::Force:
-      return "Newton";
-    case Quantity::DipoleMoment:
-      return "Coulomb * meter";
-    }
-  } else if (!strcmp(update->unit_style, "cgs")) {
-    switch (quantity) {
-    case Quantity::Unknown:
-      return "";
-    case Quantity::Time:
-      return "second";
-    case Quantity::Distance:
-      return "centimeter";
-    case Quantity::Velocity:
-      return "centimeter/second";
-    case Quantity::Force:
-      return "dynes";
-    case Quantity::DipoleMoment:
-      return "statcoul * cm";
-    }
-  } else if (!strcmp(update->unit_style, "electron")) {
-    switch (quantity) {
-    case Quantity::Unknown:
-      return "";
-    case Quantity::Time:
-      return "second";
-    case Quantity::Distance:
-      return "centimeter";
-    case Quantity::Velocity:
-      return "centimeter/second";
-    case Quantity::Force:
-      return "Hartrees/Bohr";
-    case Quantity::DipoleMoment:
-      return "Debye";
-    }
-  }
-
-  error->all(FLERR, "Unsupported unit style: {}", update->unit_style);
-  return "";
-}
-
 #endif /* defined(LMP_HAS_NETCDF) */
diff --git a/src/NETCDF/dump_netcdf.h b/src/NETCDF/dump_netcdf.h
index 07c104c445..619aad9138 100644
--- a/src/NETCDF/dump_netcdf.h
+++ b/src/NETCDF/dump_netcdf.h
@@ -29,6 +29,7 @@ DumpStyle(netcdf,DumpNetCDF);
 #include "dump_custom.h"
 
 namespace LAMMPS_NS {
+enum class Quantity;
 
 const int NC_FIELD_NAME_MAX = 100;
 const int DUMP_NC_MAX_DIMS = 100;
@@ -40,19 +41,6 @@ class DumpNetCDF : public DumpCustom {
   virtual void write();
 
  private:
-   // type of quantity for per-atom values (used to get the unit)
-   enum Quantity {
-      Unknown = 0,
-
-      Time,
-      Distance,
-      Velocity,
-      Force,
-      DipoleMoment,
-   };
-   // get the name of the unit for the given quantity
-   std::string unit_of(Quantity quantity);
-
   // per-atoms quantities (positions, velocities, etc.)
   struct nc_perat_t {
     int dims;                        // number of dimensions
diff --git a/src/NETCDF/dump_netcdf_mpiio.cpp b/src/NETCDF/dump_netcdf_mpiio.cpp
index af0f965e3c..ba16b8c0e6 100644
--- a/src/NETCDF/dump_netcdf_mpiio.cpp
+++ b/src/NETCDF/dump_netcdf_mpiio.cpp
@@ -19,6 +19,7 @@
 #if defined(LMP_HAS_PNETCDF)
 
 #include "dump_netcdf_mpiio.h"
+#include "netcdf_units.h"
 
 #include "atom.h"
 #include "comm.h"
@@ -102,7 +103,7 @@ DumpNetCDFMPIIO::DumpNetCDFMPIIO(LAMMPS *lmp, int narg, char **arg) :
     int ndims = 1;
     std::string mangled = earg[i];
     bool constant = false;
-    Quantity quantity = Quantity::Unknown;
+    Quantity quantity = Quantity::UNKNOWN;
 
     // name mangling
     // in the AMBER specification
@@ -110,12 +111,12 @@ DumpNetCDFMPIIO::DumpNetCDFMPIIO(LAMMPS *lmp, int narg, char **arg) :
       idim = mangled[0] - 'x';
       ndims = 3;
       mangled = "coordinates";
-      quantity = Quantity::Distance;
+      quantity = Quantity::DISTANCE;
     } else if ((mangled == "vx") || (mangled == "vy") || (mangled == "vz")) {
       idim = mangled[1] - 'x';
       ndims = 3;
       mangled = "velocities";
-      quantity = Quantity::Velocity;
+      quantity = Quantity::VELOCITY;
     } else if ((mangled == "xs") || (mangled == "ys") || (mangled == "zs")) {
       idim = mangled[0] - 'x';
       ndims = 3;
@@ -125,17 +126,17 @@ DumpNetCDFMPIIO::DumpNetCDFMPIIO(LAMMPS *lmp, int narg, char **arg) :
       idim = mangled[0] - 'x';
       ndims = 3;
       mangled = "unwrapped_coordinates";
-      quantity = Quantity::Distance;
+      quantity = Quantity::DISTANCE;
     } else if ((mangled == "fx") || (mangled == "fy") || (mangled == "fz")) {
       idim = mangled[1] - 'x';
       ndims = 3;
       mangled = "forces";
-      quantity = Quantity::Force;
+      quantity = Quantity::FORCE;
     } else if ((mangled == "mux") || (mangled == "muy") || (mangled == "muz")) {
       idim = mangled[2] - 'x';
       ndims = 3;
       mangled = "mu";
-      quantity = Quantity::DipoleMoment;
+      quantity = Quantity::DIPOLE_MOMENT;
     } else if (utils::strmatch(mangled, "^c_")) {
       std::size_t found = mangled.find('[');
       if (found != std::string::npos) {
@@ -423,7 +424,7 @@ void DumpNetCDFMPIIO::openfile()
         NCERRX( ncmpi_def_var(ncid, perat[i].name, xtype, 3, dims, &perat[i].var), perat[i].name );
       }
 
-      std::string unit = this->unit_of(perat[i].quantity);
+      std::string unit = get_unit_for(update->unit_style, perat[i].quantity, error);
       if (!unit.empty()) {
         NCERR( ncmpi_put_att_text(ncid, perat[i].var, NC_UNITS_STR, unit.size(), unit.c_str()) );
       }
@@ -455,10 +456,10 @@ void DumpNetCDFMPIIO::openfile()
     NCERR( ncmpi_put_att_text(ncid, NC_GLOBAL, "programVersion", strlen(lmp->version), lmp->version) );
 
     // units & scale
-    std::string unit = this->unit_of(Quantity::Time);
+    std::string unit = get_unit_for(update->unit_style, Quantity::TIME, error);
     NCERR( ncmpi_put_att_text(ncid, time_var, NC_UNITS_STR, unit.size(), unit.c_str()) );
 
-    unit = this->unit_of(Quantity::Distance);
+    unit = get_unit_for(update->unit_style, Quantity::DISTANCE, error);
     NCERR( ncmpi_put_att_text(ncid, cell_origin_var, NC_UNITS_STR, unit.size(), unit.c_str()) );
     NCERR( ncmpi_put_att_text(ncid, cell_lengths_var, NC_UNITS_STR, unit.size(), unit.c_str()) );
 
@@ -888,84 +889,4 @@ void DumpNetCDFMPIIO::ncerr(int err, const char *descr, int line)
   }
 }
 
-/* ---------------------------------------------------------------------- */
-
-std::string DumpNetCDF::unit_of(Quantity quantity) {
-  if (quantity == Quantity::Unknown) {
-    return "";
-  }
-
-  if (!strcmp(update->unit_style, "lj")) {
-    return "lj";
-  } else if (!strcmp(update->unit_style, "real")) {
-    switch (quantity) {
-    case Quantity::Time:
-      return "femtosecond";
-    case Quantity::Distance:
-      return "Angstrom";
-    case Quantity::Velocity:
-      return "Angstrom/femtosecond";
-    case Quantity::Force:
-      return "(Kcal/mol)/Angstrom)";
-    case Quantity::DipoleMoment:
-      return "e * Angstrom";
-    }
-  } else if (!strcmp(update->unit_style, "metal")) {
-    switch (quantity) {
-    case Quantity::Time:
-      return "picosecond";
-    case Quantity::Distance:
-      return "Angstrom";
-    case Quantity::Velocity:
-      return "Angstrom/picosecond";
-    case Quantity::Force:
-      return "eV/Angstrom";
-    case Quantity::DipoleMoment:
-      return "e * Angstrom";
-    }
-  } else if (!strcmp(update->unit_style, "si")) {
-    switch (quantity) {
-    case Quantity::Time:
-      return "second";
-    case Quantity::Distance:
-      return "meter";
-    case Quantity::Velocity:
-      return "meter/second";
-    case Quantity::Force:
-      return "Newton";
-    case Quantity::DipoleMoment:
-      return "Coulomb * meter";
-    }
-  } else if (!strcmp(update->unit_style, "cgs")) {
-    switch (quantity) {
-    case Quantity::Time:
-      return "second";
-    case Quantity::Distance:
-      return "centimeter";
-    case Quantity::Velocity:
-      return "centimeter/second";
-    case Quantity::Force:
-      return "dynes";
-    case Quantity::DipoleMoment:
-      return "statcoul * cm";
-    }
-  } else if (!strcmp(update->unit_style, "electron")) {
-    switch (quantity) {
-    case Quantity::Time:
-      return "second";
-    case Quantity::Distance:
-      return "centimeter";
-    case Quantity::Velocity:
-      return "centimeter/second";
-    case Quantity::Force:
-      return "Hartrees/Bohr";
-    case Quantity::DipoleMoment:
-      return "Debye";
-    }
-  }
-
-  error->all(FLERR, "Unsupported unit style: {}", update->unit_style);
-  return "";
-}
-
 #endif /* defined(LMP_HAS_PNETCDF) */
diff --git a/src/NETCDF/dump_netcdf_mpiio.h b/src/NETCDF/dump_netcdf_mpiio.h
index eb2cfb7b90..97fad9b805 100644
--- a/src/NETCDF/dump_netcdf_mpiio.h
+++ b/src/NETCDF/dump_netcdf_mpiio.h
@@ -29,6 +29,7 @@ DumpStyle(netcdf/mpiio,DumpNetCDFMPIIO);
 #include "dump_custom.h"
 
 namespace LAMMPS_NS {
+enum class Quantity;
 
 const int NC_MPIIO_FIELD_NAME_MAX = 100;
 const int DUMP_NC_MPIIO_MAX_DIMS = 100;
@@ -40,19 +41,6 @@ class DumpNetCDFMPIIO : public DumpCustom {
   virtual void write();
 
  private:
-   // type of quantity for per-atom values (used to get the unit)
-   enum Quantity {
-      Unknown = 0,
-
-      Time,
-      Distance,
-      Velocity,
-      Force,
-      DipoleMoment,
-   };
-   // get the name of the unit for the given quantity
-   std::string unit_of(Quantity quantity);
-
   // per-atoms quantities (positions, velocities, etc.)
   struct nc_perat_t {
     int dims;                              // number of dimensions
diff --git a/src/NETCDF/netcdf_units.cpp b/src/NETCDF/netcdf_units.cpp
new file mode 100644
index 0000000000..938512755a
--- /dev/null
+++ b/src/NETCDF/netcdf_units.cpp
@@ -0,0 +1,143 @@
+// clang-format off
+/* ----------------------------------------------------------------------
+   LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
+   https://www.lammps.org/, Sandia National Laboratories
+   Steve Plimpton, sjplimp@sandia.gov
+
+   Copyright (2003) Sandia Corporation.  Under the terms of Contract
+   DE-AC04-94AL85000 with Sandia Corporation, the U.S. Government retains
+   certain rights in this software.  This software is distributed under
+   the GNU General Public License.
+
+   See the README file in the top-level LAMMPS directory.
+------------------------------------------------------------------------- */
+
+/* ----------------------------------------------------------------------
+   Contributing author: Lars Pastewka (University of Freiburg)
+------------------------------------------------------------------------- */
+
+#if defined(LMP_HAS_NETCDF) || defined(LMP_HAS_PNETCDF)
+
+#include "netcdf_units.h"
+
+#include "error.h"
+
+std::string LAMMPS_NS::get_unit_for(const char* unit_style, Quantity quantity, Error* error) {
+  if (!strcmp(unit_style, "lj")) {
+    if (quantity == Quantity::UNKNOWN) {
+      return "";
+    } else {
+      return "lj";
+    }
+  } else if (!strcmp(unit_style, "real")) {
+    switch (quantity) {
+    case Quantity::UNKNOWN:
+      return "";
+    case Quantity::TIME:
+      return "femtosecond";
+    case Quantity::DISTANCE:
+      return "angstrom";
+    case Quantity::VELOCITY:
+      return "angstrom/femtosecond";
+    case Quantity::FORCE:
+      return "(Kcal/mol)/angstrom)";
+    case Quantity::DIPOLE_MOMENT:
+      return "e * angstrom";
+    }
+  } else if (!strcmp(unit_style, "metal")) {
+    switch (quantity) {
+    case Quantity::UNKNOWN:
+      return "";
+    case Quantity::TIME:
+      return "picosecond";
+    case Quantity::DISTANCE:
+      return "angstrom";
+    case Quantity::VELOCITY:
+      return "angstrom/picosecond";
+    case Quantity::FORCE:
+      return "eV/angstrom";
+    case Quantity::DIPOLE_MOMENT:
+      return "e * angstrom";
+    }
+  } else if (!strcmp(unit_style, "si")) {
+    switch (quantity) {
+    case Quantity::UNKNOWN:
+      return "";
+    case Quantity::TIME:
+      return "second";
+    case Quantity::DISTANCE:
+      return "meter";
+    case Quantity::VELOCITY:
+      return "meter/second";
+    case Quantity::FORCE:
+      return "Newton";
+    case Quantity::DIPOLE_MOMENT:
+      return "Coulomb * meter";
+    }
+  } else if (!strcmp(unit_style, "cgs")) {
+    switch (quantity) {
+    case Quantity::UNKNOWN:
+      return "";
+    case Quantity::TIME:
+      return "second";
+    case Quantity::DISTANCE:
+      return "centimeter";
+    case Quantity::VELOCITY:
+      return "centimeter/second";
+    case Quantity::FORCE:
+      return "dynes";
+    case Quantity::DIPOLE_MOMENT:
+      return "statcoul * cm";
+    }
+  } else if (!strcmp(unit_style, "electron")) {
+    switch (quantity) {
+    case Quantity::UNKNOWN:
+      return "";
+    case Quantity::TIME:
+      return "femtoseconds";
+    case Quantity::DISTANCE:
+      return "Bohr";
+    case Quantity::VELOCITY:
+      return "Bohr/atomic time units";
+    case Quantity::FORCE:
+      return "Hartree/Bohr";
+    case Quantity::DIPOLE_MOMENT:
+      return "Debye";
+    }
+  } else if (!strcmp(unit_style, "micro")) {
+    switch (quantity) {
+    case Quantity::UNKNOWN:
+      return "";
+    case Quantity::TIME:
+      return "microseconds";
+    case Quantity::DISTANCE:
+      return "micrometers";
+    case Quantity::VELOCITY:
+      return "micrometers/microsecond";
+    case Quantity::FORCE:
+      return "picogram * micrometer/microsecond^2";
+    case Quantity::DIPOLE_MOMENT:
+      return "picocoulomb * micrometer";
+    }
+  } else if (!strcmp(unit_style, "nano")) {
+    switch (quantity) {
+    case Quantity::UNKNOWN:
+      return "";
+    case Quantity::TIME:
+      return "nanoseconds";
+    case Quantity::DISTANCE:
+      return "nanometers";
+    case Quantity::VELOCITY:
+      return "nanometers/nanosecond";
+    case Quantity::FORCE:
+      return "attogram * nanometer/nanosecond^2";
+    case Quantity::DIPOLE_MOMENT:
+      return "e * nanometer";
+    }
+  }
+
+  error->all(FLERR, "Unsupported unit style: {}", unit_style);
+  return "";
+}
+
+#endif
diff --git a/src/NETCDF/netcdf_units.h b/src/NETCDF/netcdf_units.h
new file mode 100644
index 0000000000..bb83d983c8
--- /dev/null
+++ b/src/NETCDF/netcdf_units.h
@@ -0,0 +1,45 @@
+/* -*- c++ -*- ----------------------------------------------------------
+   LAMMPS - Large-scale Atomic/Molecular Massively Parallel Simulator
+   https://www.lammps.org/, Sandia National Laboratories
+   Steve Plimpton, sjplimp@sandia.gov
+
+   Copyright (2003) Sandia Corporation.  Under the terms of Contract
+   DE-AC04-94AL85000 with Sandia Corporation, the U.S. Government retains
+   certain rights in this software.  This software is distributed under
+   the GNU General Public License.
+
+   See the README file in the top-level LAMMPS directory.
+------------------------------------------------------------------------- */
+
+/* ----------------------------------------------------------------------
+   Contributing authors: Lars Pastewka (University of Freiburg), Guillaume Fraux (EPFL)
+------------------------------------------------------------------------- */
+
+#ifndef LMP_NETCDF_UNITS_H
+#define LMP_NETCDF_UNITS_H
+
+#if defined(LMP_HAS_NETCDF) || defined(LMP_HAS_PNETCDF)
+
+#include <string>
+
+namespace LAMMPS_NS {
+class Error;
+
+// type of quantity for per-atom values (used to get the unit)
+enum class Quantity {
+    UNKNOWN = 0,
+    TIME,
+    DISTANCE,
+    VELOCITY,
+    FORCE,
+    DIPOLE_MOMENT,
+};
+
+// get the name of the unit for the given `quantity` in the given LAMMPS
+// `unit_style` any error will be reported through `error`
+std::string get_unit_for(const char* unit_style, Quantity quantity, Error* error);
+
+}
+
+#endif
+#endif