diff --git a/klippy/extras/delta_calibrate.py b/klippy/extras/delta_calibrate.py
index b30ffaf2..db8509a7 100644
--- a/klippy/extras/delta_calibrate.py
+++ b/klippy/extras/delta_calibrate.py
@@ -216,12 +216,7 @@ class DeltaCalibrate:
             adj_params += ('arm_a', 'arm_b', 'arm_c')
             z_weight = len(distances) / (MEASURE_WEIGHT * len(probe_positions))
         # Perform coordinate descent
-        call_count = [0]
         def delta_errorfunc(params):
-            call_count[0] += 1
-            if not call_count[0] % 1000:
-                self.gcode.respond_info("Working on calibration...")
-                self.printer.get_reactor().pause(0.)
             # Build new delta_params for params under test
             delta_params = build_delta_params(params)
             # Calculate z height errors
@@ -237,8 +232,8 @@ class DeltaCalibrate:
                 d = math.sqrt((x1-x2)**2 + (y1-y2)**2 + (z1-z2)**2)
                 total_error += (d - dist)**2
             return total_error
-        new_params = mathutil.coordinate_descent(
-            adj_params, params, delta_errorfunc)
+        new_params = mathutil.background_coordinate_descent(
+            self.printer, adj_params, params, delta_errorfunc)
         # Log and report results
         logging.info("Calculated delta_calibrate parameters: %s", new_params)
         new_delta_params = build_delta_params(new_params)
diff --git a/klippy/mathutil.py b/klippy/mathutil.py
index 0801eba5..81a949ad 100644
--- a/klippy/mathutil.py
+++ b/klippy/mathutil.py
@@ -3,7 +3,7 @@
 # Copyright (C) 2018  Kevin O'Connor <kevin@koconnor.net>
 #
 # This file may be distributed under the terms of the GNU GPLv3 license.
-import math, logging
+import math, logging, multiprocessing
 
 
 ######################################################################
@@ -45,6 +45,33 @@ def coordinate_descent(adj_params, params, error_func):
     logging.info("Coordinate descent best_err: %s  rounds: %d", best_err, rounds)
     return params
 
+# Helper to run the coordinate descent function in a background
+# process so that it does not block the main thread.
+def background_coordinate_descent(printer, adj_params, params, error_func):
+    parent_conn, child_conn = multiprocessing.Pipe()
+    def wrapper():
+        res = coordinate_descent(adj_params, params, error_func)
+        child_conn.send(res)
+        child_conn.close()
+    # Start a process to perform the calculation
+    calc_proc = multiprocessing.Process(target=wrapper)
+    calc_proc.daemon = True
+    calc_proc.start()
+    # Wait for the process to finish
+    reactor = printer.get_reactor()
+    gcode = printer.lookup_object("gcode")
+    eventtime = last_report_time = reactor.monotonic()
+    while calc_proc.is_alive():
+        if eventtime > last_report_time + 5.:
+            last_report_time = eventtime
+            gcode.respond_info("Working on calibration...")
+        eventtime = reactor.pause(eventtime + .1)
+    # Return results
+    res = parent_conn.recv()
+    calc_proc.join()
+    parent_conn.close()
+    return res
+
 
 ######################################################################
 # Trilateration