diff --git a/server/src/lib/score-import/framework/calculated-data/calculated-data.ts b/server/src/lib/score-import/framework/calculated-data/calculated-data.ts
index 8bc2e0340..a169eacbc 100644
--- a/server/src/lib/score-import/framework/calculated-data/calculated-data.ts
+++ b/server/src/lib/score-import/framework/calculated-data/calculated-data.ts
@@ -15,7 +15,7 @@ import {
 	CalculateBPI,
 	CalculateCHUNITHMRating,
 	CalculateGITADORASkill,
-	CalculateKTLampRating,
+	CalculateKTLampRatingIIDX,
 	CalculateKTRating,
 	CalculateMFCP,
 	CalculateVF6,
@@ -136,7 +136,7 @@ async function CalculateDataIIDXSP(
 			BPIData.kavg,
 			BPIData.wr,
 			dryScore.scoreData.score,
-			(chart as ChartDocument<"iidx:DP" | "iidx:SP">).data.notecount * 2,
+			(chart as ChartDocument<"iidx:SP">).data.notecount * 2,
 			BPIData.coef
 		);
 
@@ -147,8 +147,8 @@ async function CalculateDataIIDXSP(
 
 	return {
 		BPI: bpi,
-		ktRating: await CalculateKTRating(dryScore, "iidx", "SP", chart, logger),
-		ktLampRating: await CalculateKTLampRating(dryScore, "iidx", "SP", chart),
+		ktRating: CalculateKTRating(dryScore, "iidx", "SP", chart, logger),
+		ktLampRating: CalculateKTLampRatingIIDX(dryScore, "SP", chart as ChartDocument<"iidx:SP">),
 	};
 }
 
@@ -168,7 +168,7 @@ async function CalculateDataIIDXDP(
 			BPIData.kavg,
 			BPIData.wr,
 			dryScore.scoreData.score,
-			(chart as ChartDocument<"iidx:DP" | "iidx:SP">).data.notecount * 2,
+			(chart as ChartDocument<"iidx:DP">).data.notecount * 2,
 			BPIData.coef
 		);
 
@@ -179,8 +179,8 @@ async function CalculateDataIIDXDP(
 
 	return {
 		BPI: bpi,
-		ktRating: await CalculateKTRating(dryScore, "iidx", "DP", chart, logger),
-		ktLampRating: await CalculateKTLampRating(dryScore, "iidx", "DP", chart),
+		ktRating: CalculateKTRating(dryScore, "iidx", "DP", chart, logger),
+		ktLampRating: CalculateKTLampRatingIIDX(dryScore, "DP", chart as ChartDocument<"iidx:DP">),
 	};
 }
 
diff --git a/server/src/lib/score-import/framework/calculated-data/stats.test.ts b/server/src/lib/score-import/framework/calculated-data/stats.test.ts
index 6121ae303..8d157ad0f 100644
--- a/server/src/lib/score-import/framework/calculated-data/stats.test.ts
+++ b/server/src/lib/score-import/framework/calculated-data/stats.test.ts
@@ -9,6 +9,7 @@ import {
 	CalculateBPI,
 	CalculateCHUNITHMRating,
 	CalculateGITADORASkill,
+	CalculateKTLampRatingIIDX,
 	CalculateKTRating,
 	CalculateMFCP,
 	CalculateVF6,
@@ -110,6 +111,98 @@ t.test("#CalculateBPI", (t) => {
 	t.end();
 });
 
+t.test("#CalculateKTLampRatingIIDx", (t) => {
+	function c(
+		nc: number | null,
+		hc: number | null,
+		exhc: number | null
+	): ChartDocument<"iidx:SP"> {
+		return Object.assign({}, Testing511SPA, {
+			tierlistInfo: {
+				"kt-EXHC": {
+					value: exhc,
+				},
+				"kt-HC": {
+					value: hc,
+				},
+				"kt-NC": {
+					value: nc,
+				},
+			},
+		});
+	}
+
+	function s(lamp: Lamps["iidx:SP" | "iidx:DP"]): DryScore<"iidx:SP" | "iidx:DP"> {
+		return Object.assign({}, TestingIIDXSPDryScore, {
+			scoreData: {
+				lamp,
+			},
+		});
+	}
+
+	t.equal(
+		CalculateKTLampRatingIIDX(s("CLEAR"), "SP", c(10.5, 10.6, 10.7)),
+		10.5,
+		"Should return NC if the score was NC."
+	);
+
+	t.equal(
+		CalculateKTLampRatingIIDX(s("HARD CLEAR"), "SP", c(10.5, 10.6, 10.7)),
+		10.6,
+		"Should return HC if the score was HC."
+	);
+
+	t.equal(
+		CalculateKTLampRatingIIDX(s("EX HARD CLEAR"), "SP", c(10.5, 10.6, 10.7)),
+		10.7,
+		"Should return EXHC if the score was EXHC."
+	);
+
+	t.equal(
+		CalculateKTLampRatingIIDX(s("CLEAR"), "SP", c(null, 10.6, 10.7)),
+		0,
+		"Should return 0 if the score was NC but no NC was available."
+	);
+
+	t.equal(
+		CalculateKTLampRatingIIDX(s("HARD CLEAR"), "SP", c(null, null, 10.7)),
+		0,
+		"Should return 0 if the score was HC but no HC or NC was available."
+	);
+
+	tequal(
+		CalculateKTLampRatingIIDX(s("HARD CLEAR"), "SP", c(10.5, null, 10.7)),
+		10.5,
+		"Should return NC if the score was HC but no HC was available."
+	);
+
+	t.equal(
+		CalculateKTLampRatingIIDX(s("HARD CLEAR"), "SP", c(10.9, 10.5, 10.7)),
+		10.9,
+		"Should return NC if the score was HC but NC was worth more."
+	);
+
+	t.equal(
+		CalculateKTLampRatingIIDX(s("EX HARD CLEAR"), "SP", c(10.9, 10.5, 10.7)),
+		10.9,
+		"Should return NC if the score was EXHC but NC was worth more."
+	);
+
+	t.equal(
+		CalculateKTLampRatingIIDX(s("EX HARD CLEAR"), "SP", c(10.4, 10.9, 10.7)),
+		10.9,
+		"Should return HC if the score was EXHC but HC was worth more."
+	);
+
+	t.equal(
+		CalculateKTLampRatingIIDX(s("CLEAR"), "SP", c(null, null, null)),
+		10,
+		"Should return chart level if the chart has no tierlist data."
+	);
+
+	t.end();
+});
+
 t.test("#CalculateGITADORARating", (t) => {
 	function TestGitadoraRating(percent: number, levelNum: number) {
 		return CalculateGITADORASkill(
diff --git a/server/src/lib/score-import/framework/calculated-data/stats.ts b/server/src/lib/score-import/framework/calculated-data/stats.ts
index 67714211a..8f6c9e621 100644
--- a/server/src/lib/score-import/framework/calculated-data/stats.ts
+++ b/server/src/lib/score-import/framework/calculated-data/stats.ts
@@ -4,6 +4,7 @@ import {
 	Game,
 	GetGamePTConfig,
 	Grades,
+	IIDX_LAMPS,
 	integer,
 	Lamps,
 	Playtypes,
@@ -317,13 +318,34 @@ export function CalculateKTRating(
 	return KTRatingCalcV1(dryScore.scoreData.percent, levelNum, parameters, logger);
 }
 
-export function CalculateKTLampRating(
+export function CalculateKTLampRatingIIDX(
 	dryScore: DryScore,
-	game: Game,
 	playtype: Playtypes[Game],
-	chart: ChartDocument
+	chart: ChartDocument<"iidx:SP" | "iidx:DP">
 ) {
-	return LampRatingNoTierlistInfo(dryScore, game, playtype, chart);
+	const ncValue = chart.tierlistInfo["kt-NC"]?.value ?? 0;
+	const hcValue = Math.max(chart.tierlistInfo["kt-HC"]?.value ?? 0, ncValue);
+	const exhcValue = Math.max(chart.tierlistInfo["kt-EXHC"]?.value ?? 0, hcValue);
+
+	if (!exhcValue && !hcValue && !ncValue) {
+		return LampRatingNoTierlistInfo(dryScore, "iidx", playtype, chart);
+	}
+
+	const lamp = dryScore.scoreData.lamp;
+
+	const gptConfig = GetGamePTConfig("iidx", playtype);
+
+	const lampIndex = gptConfig.lamps.indexOf(lamp);
+
+	if (exhcValue && lampIndex >= IIDX_LAMPS.EX_HARD_CLEAR) {
+		return exhcValue;
+	} else if (hcValue && lampIndex >= IIDX_LAMPS.HARD_CLEAR) {
+		return hcValue;
+	} else if (ncValue && lampIndex >= IIDX_LAMPS.CLEAR) {
+		return ncValue;
+	}
+
+	return 0;
 }
 
 function LampRatingNoTierlistInfo(