diff --git a/docs/Config_Changes.md b/docs/Config_Changes.md
index e9bcd120..ead2445c 100644
--- a/docs/Config_Changes.md
+++ b/docs/Config_Changes.md
@@ -8,6 +8,12 @@ All dates in this document are approximate.
 
 ## Changes
 
+20220116: The tmc2130, tmc2208, tmc2209, and tmc2660 `run_current`
+calculation code has changed. For some `run_current` settings the
+drivers may now be configured differently. This new configuration
+should be more accurate, but it may invalidate previous tmc driver
+tuning.
+
 20211230: Scripts to tune input shaper (`scripts/calibrate_shaper.py`
 and `scripts/graph_accelerometer.py`) were migrated to use Python3
 by default. As a result, users must install Python3 versions of certain
diff --git a/klippy/extras/tmc2130.py b/klippy/extras/tmc2130.py
index c6a54561..f2142d26 100644
--- a/klippy/extras/tmc2130.py
+++ b/klippy/extras/tmc2130.py
@@ -116,30 +116,33 @@ class TMCCurrentHelper:
         vref = 0.32
         if vsense:
             vref = 0.18
-        cs = int(32. * current * sense_resistor * math.sqrt(2.) / vref
-                 - 1. + .5)
+        cs = int(32. * sense_resistor * current * math.sqrt(2.) / vref + .5) - 1
         return max(0, min(31, cs))
-    def _calc_current(self, run_current, hold_current):
-        vsense = False
-        irun = self._calc_current_bits(run_current, vsense)
-        ihold = self._calc_current_bits(min(hold_current, run_current),
-                                        vsense)
-        if irun < 16 and ihold < 16:
-            vsense = True
-            irun = self._calc_current_bits(run_current, vsense)
-            ihold = self._calc_current_bits(min(hold_current, run_current),
-                                            vsense)
-        return vsense, irun, ihold
-    def _calc_current_from_field(self, field_name):
-        bits = self.fields.get_field(field_name)
+    def _calc_current_from_bits(self, cs, vsense):
         sense_resistor = self.sense_resistor + 0.020
         vref = 0.32
-        if self.fields.get_field("vsense"):
+        if vsense:
             vref = 0.18
-        return (bits + 1) * vref / (32 * sense_resistor * math.sqrt(2.))
+        return (cs + 1) * vref / (32. * sense_resistor * math.sqrt(2.))
+    def _calc_current(self, run_current, hold_current):
+        vsense = True
+        irun = self._calc_current_bits(run_current, True)
+        if irun == 31:
+            cur = self._calc_current_from_bits(irun, True)
+            if cur < run_current:
+                irun2 = self._calc_current_bits(run_current, False)
+                cur2 = self._calc_current_from_bits(irun2, False)
+                if abs(run_current - cur2) < abs(run_current - cur):
+                    vsense = False
+                    irun = irun2
+        ihold = self._calc_current_bits(min(hold_current, run_current), vsense)
+        return vsense, irun, ihold
     def get_current(self):
-        run_current = self._calc_current_from_field("irun")
-        hold_current = self._calc_current_from_field("ihold")
+        irun = self.fields.get_field("irun")
+        ihold = self.fields.get_field("ihold")
+        vsense = self.fields.get_field("vsense")
+        run_current = self._calc_current_from_bits(irun, vsense)
+        hold_current = self._calc_current_from_bits(ihold, vsense)
         return run_current, hold_current, self.req_hold_current, MAX_CURRENT
     def set_current(self, run_current, hold_current, print_time):
         self.req_hold_current = hold_current
diff --git a/klippy/extras/tmc2660.py b/klippy/extras/tmc2660.py
index c0d8fa9b..e873c608 100644
--- a/klippy/extras/tmc2660.py
+++ b/klippy/extras/tmc2660.py
@@ -136,17 +136,26 @@ class TMC2660CurrentHelper:
 
     def _calc_current_bits(self, current, vsense):
         vref = 0.165 if vsense else 0.310
-        cs = int(32 * current * self.sense_resistor * math.sqrt(2.) / vref
-                 - 1. + .5)
+        sr = self.sense_resistor
+        cs = int(32. * sr * current * math.sqrt(2.) / vref + .5) - 1
         return max(0, min(31, cs))
 
+    def _calc_current_from_bits(self, cs, vsense):
+        vref = 0.165 if vsense else 0.310
+        return (cs + 1) * vref / (32. * self.sense_resistor * math.sqrt(2.))
+
     def _calc_current(self, run_current):
-        vsense = False
-        cs = self._calc_current_bits(run_current, vsense)
-        if cs < 16:
-            vsense = True
-            cs = self._calc_current_bits(run_current, vsense)
-        return vsense, cs
+        vsense = True
+        irun = self._calc_current_bits(run_current, True)
+        if irun == 31:
+            cur = self._calc_current_from_bits(irun, True)
+            if cur < run_current:
+                irun2 = self._calc_current_bits(run_current, False)
+                cur2 = self._calc_current_from_bits(irun2, False)
+                if abs(run_current - cur2) < abs(run_current - cur):
+                    vsense = False
+                    irun = irun2
+        return vsense, irun
 
     def _handle_printing(self, print_time):
         print_time -= 0.100 # Schedule slightly before deadline