diff --git a/Sources/LoopAlgorithm/Experiments/GuardAndRunwayOutput.swift b/Sources/LoopAlgorithm/Experiments/GuardAndRunwayOutput.swift
index 5afe682..2c80b00 100644
--- a/Sources/LoopAlgorithm/Experiments/GuardAndRunwayOutput.swift
+++ b/Sources/LoopAlgorithm/Experiments/GuardAndRunwayOutput.swift
@@ -13,6 +13,9 @@ public struct GuardAndRunwayOutput: Equatable {
     public var volatility: Double
     /// False when active carbs kept the volatility band off.
     public var bandApplied: Bool
+    /// The most the band lowered any point of the forecast, mg/dL; 0 when it was off. A forecast with no
+    /// points near 60 min, where the band is deepest, is lowered less.
+    public var bandDepth: Double
     /// How far the target for automatic dosing was lowered, mg/dL. Manual recommendations keep the target.
     public var runwayShift: Double
     /// True while the post-low cut scales down the rising side of retrospective correction.
@@ -23,11 +26,6 @@ public struct GuardAndRunwayOutput: Equatable {
     /// The band's depth multiplier, from the volatility baseline.
     public var bandGain: Double { band.gain }
 
-    /// How far the band lowers the forecast at its deepest point (60 min), mg/dL; 0 when it was off.
-    public var bandDepth: Double {
-        bandApplied ? band.gain * volatility * pow(band.horizon.minutes / 5.0, band.exponent) : 0
-    }
-
     /// `glucose` lowered by the band as this run applied it; unchanged when the band was off.
     public func guarded(_ glucose: [PredictedGlucoseValue]) -> [PredictedGlucoseValue] {
         bandApplied ? LoopAlgorithm.volatilityBanded(glucose, band: band, volatility: volatility) : glucose
diff --git a/Sources/LoopAlgorithm/LoopAlgorithm.swift b/Sources/LoopAlgorithm/LoopAlgorithm.swift
index e5a3fa1..378f0e5 100644
--- a/Sources/LoopAlgorithm/LoopAlgorithm.swift
+++ b/Sources/LoopAlgorithm/LoopAlgorithm.swift
@@ -842,11 +842,16 @@ public struct LoopAlgorithm {
             }
             if let band = experimentParameters.volatilityBand, let volatility {
                 let bandApplied = !(band.carbGate && (prediction.activeCarbs ?? 0) > 0)
+                var bandDepth = 0.0
                 if bandApplied {
-                    prediction.glucose = volatilityBanded(prediction.glucose, band: band, volatility: volatility)
+                    let banded = volatilityBanded(prediction.glucose, band: band, volatility: volatility)
+                    bandDepth = zip(prediction.glucose, banded).map {
+                        $0.quantity.doubleValue(for: .milligramsPerDeciliter) - $1.quantity.doubleValue(for: .milligramsPerDeciliter)
+                    }.max() ?? 0
+                    prediction.glucose = banded
                 }
                 guardAndRunway = GuardAndRunwayOutput(
-                    volatility: volatility, bandApplied: bandApplied, runwayShift: runwayShift,
+                    volatility: volatility, bandApplied: bandApplied, bandDepth: bandDepth, runwayShift: runwayShift,
                     postLowRiseCutActive: experimentParameters.postLowRiseCut?.isActive(glucoseHistory: input.glucoseHistory) ?? false,
                     band: band)
             }
diff --git a/Tests/LoopAlgorithmTests/AlgorithmExperimentsTests.swift b/Tests/LoopAlgorithmTests/AlgorithmExperimentsTests.swift
index 5ea3fa9..45ab34b 100644
--- a/Tests/LoopAlgorithmTests/AlgorithmExperimentsTests.swift
+++ b/Tests/LoopAlgorithmTests/AlgorithmExperimentsTests.swift
@@ -248,8 +248,7 @@ final class AlgorithmExperimentsTests: XCTestCase {
             XCTAssertFalse(output.postLowRiseCutActive)
             XCTAssertEqual(output.guarded(standard.predictedGlucose), runway.predictedGlucose)
             let deepest = zip(plain, banded).map { $0 - $1 }.max()!
-            XCTAssertLessThanOrEqual(deepest, output.bandDepth + 1e-9)
-            XCTAssertGreaterThan(deepest, 0.9 * output.bandDepth, "forecast points fall near the 60 min horizon")
+            XCTAssertEqual(output.bandDepth, deepest, accuracy: 1e-9)
             if type == .tempBasal {
                 XCTAssertGreaterThan(runway.recommendation!.automatic!.basalAdjustment.unitsPerHour,
                                      standard.recommendation!.automatic!.basalAdjustment.unitsPerHour)