diff --git a/doc/source/firmware/pt1000-processing.rst b/doc/source/firmware/pt1000-processing.rst
index 492d232..cfd9e50 100644
--- a/doc/source/firmware/pt1000-processing.rst
+++ b/doc/source/firmware/pt1000-processing.rst
@@ -132,7 +132,7 @@ and
 .. doxygenfunction:: adc_pt1000_get_resistance_calibration
 	:outline:
 
-are used to set the reistance calibration internally. For a guide on how to calibrate the deivce, see the corresponding :ref:`usage_calibration` usage page.
+are used to set the resistance calibration internally. For a guide on how to calibrate the deivce, see the corresponding :ref:`usage_calibration` usage page.
 
 The calibration is calculated the following way:
 
@@ -147,13 +147,13 @@ The calibration is calculated the following way:
 		OFFSET [label="Offset", description="Offset Correction :math:`O`"];
 		OUT [shape=endpoint, description="Corrected Value"];
 
-		LF -> SENS -> OFFSET -> OUT
+		LF -> OFFSET -> SENS -> OUT
 	}
 
 The final calibrated PT1000 resistance is calculated as:
 
 .. math::
-	R_{PT1000_{corr}} = R_{PT1000_{LF}} \cdot (1 + \sigma) + O
+	R_{PT1000_{corr}} = (R_{PT1000_{LF}} - O) \cdot (1 + \sigma)
 
 The default values, if no calibration is loaded / executed, are:
 
diff --git a/stm-firmware/.gitignore b/stm-firmware/.gitignore
index cfdd888..1e70134 100644
--- a/stm-firmware/.gitignore
+++ b/stm-firmware/.gitignore
@@ -14,3 +14,4 @@ reflow-controller.includes
 *.includes
 *.config
 *.files
+*.user.*
diff --git a/stm-firmware/adc-meas.c b/stm-firmware/adc-meas.c
index 4a9f0e3..816b993 100644
--- a/stm-firmware/adc-meas.c
+++ b/stm-firmware/adc-meas.c
@@ -216,7 +216,7 @@ void adc_pt1000_get_resistance_calibration(float *offset, float *sensitivity_dev
 static inline float adc_pt1000_apply_calibration(float raw_resistance)
 {
 	if (calibration_active)
-		return pt1000_res_raw_lf * (1.0f + pt1000_sens_dev) + pt1000_offset;
+        return (raw_resistance - pt1000_offset) * (1.0f + pt1000_sens_dev);
 	else
 		return raw_resistance;
 
diff --git a/stm-firmware/calibration.c b/stm-firmware/calibration.c
index 81dd815..35f3509 100644
--- a/stm-firmware/calibration.c
+++ b/stm-firmware/calibration.c
@@ -30,9 +30,9 @@
 enum calibration_shell_state {CAL_START = 0, CAL_WAIT_RES1, CAL_MEAS_RES1, CAL_WAIT_RES2, CAL_MEAS_RES2};
 
 void calibration_calculate(float low_measured, float low_setpoint, float high_measured, float high_setpoint,
-			   float *sens_deviation, float *sens_corrected_offset)
+			   float *sens_deviation, float *offset)
 {
-	if (!sens_deviation || !sens_corrected_offset)
+	if (!sens_deviation || !offset)
 		return;
 
 	float delta_y;
@@ -45,7 +45,7 @@ void calibration_calculate(float low_measured, float low_setpoint, float high_me
 	sens_corr_mult = delta_x / delta_y;
 	*sens_deviation = sens_corr_mult - 1.0f;
 
-	*sens_corrected_offset = low_setpoint - low_measured * sens_corr_mult;
+	*offset = (high_setpoint * low_measured - low_setpoint * high_measured) / (high_setpoint - low_setpoint);
 }
 
 
diff --git a/stm-firmware/include/reflow-controller/calibration.h b/stm-firmware/include/reflow-controller/calibration.h
index cb7fd2e..78ab5f3 100644
--- a/stm-firmware/include/reflow-controller/calibration.h
+++ b/stm-firmware/include/reflow-controller/calibration.h
@@ -27,7 +27,7 @@
 #include <shellmatta.h>
 
 void calibration_calculate(float low_measured, float low_setpoint, float high_measured, float high_setpoint,
-			   float *sens_deviation, float *sens_corrected_offset);
+			   float *sens_deviation, float *offset);
 
 float *calibration_acquire_data_start(uint32_t count, volatile int *flag);