diff --git a/zeitlaeufer/src/main/java/de/szimnau/DrinkingBar.java b/zeitlaeufer/src/main/java/de/szimnau/DrinkingBar.java
index e51e890..0ec61aa 100644
--- a/zeitlaeufer/src/main/java/de/szimnau/DrinkingBar.java
+++ b/zeitlaeufer/src/main/java/de/szimnau/DrinkingBar.java
@@ -6,6 +6,8 @@ import java.io.BufferedReader;
 import java.io.InputStreamReader;
 import java.io.IOException;
 import java.math.BigDecimal;
+import java.math.MathContext;
+import java.math.RoundingMode;
 import java.nio.charset.StandardCharsets;
 import java.text.DecimalFormat;
 import java.time.LocalTime;
@@ -20,16 +22,17 @@ public class DrinkingBar extends AbstractLoadingBar {
    private static final int MINUTES_BEFORE_PAUSE = 4 * CommonTools.MINS_PER_HOUR + MINS_PER_HALF_HOUR;
    private static final int MINUTES_WITH_PAUSE = 6 * CommonTools.MINS_PER_HOUR;
    private static final int DEFAULT_TOTAL_TIME = 8 * CommonTools.MINS_PER_HOUR + MINS_PER_HALF_HOUR;
-   private static final double DEFAULT_TOTAL_LITRES = 2.0;
-   private static final double QUARTER_LITRE = 0.25;
+   private static final BigDecimal DEFAULT_TOTAL_TIME_BD = BigDecimal.valueOf(DEFAULT_TOTAL_TIME);
+   private static final BigDecimal DEFAULT_TOTAL_LITRES = BigDecimal.valueOf(2.0);
+   private static final BigDecimal QUARTER_LITRE = BigDecimal.valueOf(0.25);
    private static final DecimalFormat LITER_FORMAT = new DecimalFormat("0.00");
 
-   private double totalLitres;
+   private BigDecimal totalLitresBD;
 
 
    protected DrinkingBar(LocalTime startTime) {
       super(startTime, DEFAULT_TOTAL_TIME);
-      this.totalLitres = DEFAULT_TOTAL_LITRES;
+      this.totalLitresBD = DEFAULT_TOTAL_LITRES;
    }
 
 
@@ -38,13 +41,15 @@ public class DrinkingBar extends AbstractLoadingBar {
       super.setEndTime(endTime);
       // correct necessary litres to drink based on the end time.
       // lower the volume in quarter litre steps
-      double calcTotalLitres = DEFAULT_TOTAL_LITRES;
-      double totalLitresFromMinutes = calcTotalLitres / DEFAULT_TOTAL_TIME * getTotalMinutes();
+      BigDecimal calcTotalLitres = DEFAULT_TOTAL_LITRES;
+      BigDecimal totalLitresFromMinutes = DEFAULT_TOTAL_LITRES
+         .multiply(getTotalMinutesBD()) // reverse dreisatz
+         .divide(DEFAULT_TOTAL_TIME_BD, MathContext.DECIMAL64);
       do {
-         calcTotalLitres -= QUARTER_LITRE;
-      } while (calcTotalLitres >= totalLitresFromMinutes);
+         calcTotalLitres = calcTotalLitres.subtract(QUARTER_LITRE);
+      } while (calcTotalLitres.compareTo(totalLitresFromMinutes) >= 0);
       // add quarter since we always did a step "too many", due to the do ... while loop
-      this.totalLitres = calcTotalLitres + QUARTER_LITRE;
+      this.totalLitresBD = calcTotalLitres.add(QUARTER_LITRE);
    }
 
 
@@ -59,13 +64,19 @@ public class DrinkingBar extends AbstractLoadingBar {
 
    @Override
    protected String fillLoadingBar(long passedMinutes, boolean progressive) {
-      long effectivePassedMinutes = passedMinutes;
+      long effectivePassedMinutes = passedMinutes < 0 ? 0 : passedMinutes;
       if (getTotalMinutes() > MINUTES_WITH_PAUSE && passedMinutes > MINUTES_BEFORE_PAUSE && passedMinutes <= MINUTES_WITH_PAUSE) {
          effectivePassedMinutes = MINUTES_BEFORE_PAUSE;
       }
-      double currentLitres = totalLitres / getTotalMinutes() * effectivePassedMinutes + QUARTER_LITRE;
-      double printedLitres = currentLitres - (currentLitres % QUARTER_LITRE);
-      // double currentProgressToNextStep = 100 / QUARTER_LITRE * (currentLitres - printedLitres);
+      var effectivePassedMinutesBD = BigDecimal.valueOf(effectivePassedMinutes);
+      BigDecimal currentLitres = totalLitresBD
+         .multiply(effectivePassedMinutesBD) // reverse dreisatz
+         .divide(getTotalMinutesBD(), MathContext.DECIMAL64)
+         .add(QUARTER_LITRE);
+      BigDecimal printedLitres = currentLitres.subtract(currentLitres.remainder(QUARTER_LITRE, MathContext.DECIMAL64));
+      /* BigDecimal currentProgressToNextStep = ONE_HUNDRED_PERCENT
+         .multiply(currentLitres.subtract(printedLitres)) // reverse dreisatz
+         .divide(QUARTER_LITRE, MathContext.DECIMAL64); */
       BigDecimal minutesToNextStep = getMinutesToNextStep(currentLitres);
       String progressivePart = progressive ? "\r" : "";
       return progressivePart + "Aktuelles Volumen: " + LITER_FORMAT.format(printedLitres) + "L - "
@@ -74,13 +85,12 @@ public class DrinkingBar extends AbstractLoadingBar {
    }
 
 
-   private BigDecimal getMinutesToNextStep(double currentLitres) {
+   private BigDecimal getMinutesToNextStep(BigDecimal currentLitres) {
       // berechne Liter benötigt bis zum nächsten 0.25er Schritt
-      double litresToNextStep = QUARTER_LITRE - (currentLitres % QUARTER_LITRE);
+      BigDecimal litresToNextStep = QUARTER_LITRE.subtract(currentLitres.remainder(QUARTER_LITRE));
       // berechne Minuten benötigt für 1 Liter
-      double minutesPerLitre = getTotalMinutes() / totalLitres;
+      BigDecimal minutesPerLitre = getTotalMinutesBD().divide(totalLitresBD);
       // berechne Minuten benötigt bis zum nächsten 0.25er Schritt
-      // + 1 since we only show minutes and have to adjust for the "ignored" seconds
-      return BigDecimal.valueOf((minutesPerLitre * litresToNextStep) + 1);
+      return minutesPerLitre.multiply(litresToNextStep).setScale(0, RoundingMode.HALF_EVEN);
    }
 }