diff --git a/code/modules/surgery/surgery_step.dm b/code/modules/surgery/surgery_step.dm
index 336e76b4d70c2f..629b67769dc2f7 100644
--- a/code/modules/surgery/surgery_step.dm
+++ b/code/modules/surgery/surgery_step.dm
@@ -130,7 +130,7 @@
 	var/modded_time = time * speed_mod
 
 
-	fail_prob = min(max(0, modded_time - (time * SURGERY_SLOWDOWN_CAP_MULTIPLIER)),99)//if modded_time > time * modifier, then fail_prob = modded_time - time*modifier. starts at 0, caps at 99
+	fail_prob = get_failure_probability(user,target,tool,modded_time,)//if modded_time > time * modifier, then fail_prob = modded_time - time*modifier. starts at 0, caps at 99
 	modded_time = min(modded_time, time * SURGERY_SLOWDOWN_CAP_MULTIPLIER)//also if that, then cap modded_time at time*modifier
 
 	if(iscyborg(user))//any immunities to surgery slowdown should go in this check.
diff --git a/modular_bandastation/medical/_medical.dme b/modular_bandastation/medical/_medical.dme
index 3783e0393c8c7a..7c801faa1c429b 100644
--- a/modular_bandastation/medical/_medical.dme
+++ b/modular_bandastation/medical/_medical.dme
@@ -1,3 +1,4 @@
 #include "_medical.dm"
 
 #include "code/surgery/vocal_cords.dm"
+#include "code/surgery/surgery_fail_chance.dm"
diff --git a/modular_bandastation/medical/code/surgery/surgery_fail_chance.dm b/modular_bandastation/medical/code/surgery/surgery_fail_chance.dm
new file mode 100644
index 00000000000000..356b98716d7c88
--- /dev/null
+++ b/modular_bandastation/medical/code/surgery/surgery_fail_chance.dm
@@ -0,0 +1,25 @@
+#define SURGFAIL_LIGHT_AMOUNT_REQUERED 0.6
+#define SURGFAIL_LIGHT_AMOUNT_MULTIPLIER 20
+#define SURGFAIL_NO_PAINKILLER 80
+#define BASIC_SURGERY_SUCCESS_CHANCE 100
+#define CRITICAL_SUCCESS_CHANCE 100
+
+
+/datum/surgery_step/proc/get_failure_probability(mob/living/user, mob/living/target, obj/item/tool, var/modded_time)
+	var/success_prob = implement_type ? implements[implement_type] : BASIC_SURGERY_SUCCESS_CHANCE
+	var/turf/user_turf = get_turf(user)
+	var/light_amount = user_turf.get_lumcount()
+	if (light_amount < SURGFAIL_LIGHT_AMOUNT_REQUERED)
+		success_prob -= (SURGFAIL_LIGHT_AMOUNT_REQUERED - clamp(light_amount, 0, SURGFAIL_LIGHT_AMOUNT_REQUERED)) * SURGFAIL_LIGHT_AMOUNT_MULTIPLIER
+	if ((!(target.stat == UNCONSCIOUS || target.IsSleeping()) && target.stat != DEAD) && !HAS_TRAIT(target, TRAIT_ANALGESIA))
+		success_prob -= SURGFAIL_NO_PAINKILLER
+	var/fail_prob = CRITICAL_SUCCESS_CHANCE - success_prob
+	fail_prob *= modded_time / time
+
+	return fail_prob
+
+#undef SURGFAIL_LIGHT_AMOUNT_REQUERED
+#undef SURGFAIL_LIGHT_AMOUNT_MULTIPLIER
+#undef SURGFAIL_NO_PAINKILLER
+#undef BASIC_SURGERY_SUCCESS_CHANCE
+#undef CRITICAL_SUCCESS_CHANCE