diff --git a/fhem/FHEM/10_CUL_HM.pm b/fhem/FHEM/10_CUL_HM.pm
index 4de717798..e1e3dd619 100755
--- a/fhem/FHEM/10_CUL_HM.pm
+++ b/fhem/FHEM/10_CUL_HM.pm
@@ -129,7 +129,8 @@ CUL_HM_Initialize($)
                        "subType:switch,dimmer,blindActuator,remote,sensor,".
                          "swi,pushButton,threeStateSensor,motionDetector,".
                          "keyMatic,winMatic,smokeDetector " .
-                       "hmClass:receiver,sender serialNr firmware devInfo";
+                       "hmClass:receiver,sender serialNr firmware devInfo ".
+                       "rawToReadable unit";
 }
 
 
@@ -499,9 +500,26 @@ Log 1, "WM2";
       my ($k_cnt, $k_v1, $k_v2, $k_v3) = ($1,$2,$3,$4);
       my $v = 128-hex($k_v2);                  # FIXME: calibrate
       $v = 256+$v if($v < 0);
-
+      $v += 256 if(!($k_v3 & 1));
       push @event, "rawValue:$v";
 
+      my $r2r = AttrVal($name, "rawToReadable", undef);
+      if($r2r) {
+        my @r2r = split("[ :]", $r2r);
+        foreach(my $idx = 0; $idx < @r2r-2; $idx+=2) {
+          if($v >= $r2r[$idx] && $v <= $r2r[$idx+2]) {
+            my $f = (($v-$r2r[$idx])/($r2r[$idx+2]-$r2r[$idx]));
+            my $cv = ($r2r[$idx+3]-$r2r[$idx+1])*$f + $r2r[$idx+1];
+            my $unit = AttrVal($name, "unit", "");
+            $unit = " $unit" if($unit);
+            push @event, "state:$cv$unit";
+            last;
+          }
+        }
+      } else {
+        push @event, "state:$v";
+      }
+
     }
 
   }
diff --git a/fhem/docs/commandref.html b/fhem/docs/commandref.html
index 1e73303be..bc0b41c8b 100644
--- a/fhem/docs/commandref.html
+++ b/fhem/docs/commandref.html
@@ -2502,6 +2502,25 @@ A line ending with \ will be concatenated with the next one, so long lines
         These attributes are set automatically after a successful pairing.
         They are not supposed to be set by hand, and are necessary in order to
         correctly interpret device messages or to be able to send them.</li>
+    <li><a name="#rawToReadable">rawToReadable</a><br>
+        Used to convert raw KFM100 values to readable data, based on measured
+        values. E.g.  fill slowly your container, while monitoring the
+        values reported with <a href="#inform">inform</a>. You'll see:
+        <ul>
+          10 (at 0%)<br>
+          50 (at 20%)<br>
+          79 (at 40%)<br>
+         270 (at 100%)<br>
+        </ul>
+        Apply these values with: "attr KFM100 rawToReadable 10:0 50:20 79:40 270:100".
+        fhem will do a linear interpolation for values between the bounderies.
+        </li>
+    <li><a name="#unit">unit</a><br>
+        set the reported unit by the KFM100 if rawToReadable is active. E.g.<br>
+        attr KFM100 unit Liter
+        </li>
+
+
 
   </ul>
   <br>