diff --git a/apps/api/src/app/portfolio/calculator/roai/portfolio-calculator-btceur.spec.ts b/apps/api/src/app/portfolio/calculator/roai/portfolio-calculator-btceur.spec.ts
index 3e26ed8b5..ba818eb40 100644
--- a/apps/api/src/app/portfolio/calculator/roai/portfolio-calculator-btceur.spec.ts
+++ b/apps/api/src/app/portfolio/calculator/roai/portfolio-calculator-btceur.spec.ts
@@ -149,8 +149,8 @@ describe('PortfolioCalculator', () => {
         date: '2021-12-12',
         investmentValueWithCurrencyEffect: 44558.42,
         netPerformance: 5535.42, // 1 * (50098.3 - 44558.42) - 4.46 = 5535.42
-        netPerformanceInPercentage: 0,
-        netPerformanceInPercentageWithCurrencyEffect: 0,
+        netPerformanceInPercentage: 0.12422837255001412, // 5535.42 ÷ 44558.42 = 0.12422837255001412
+        netPerformanceInPercentageWithCurrencyEffect: 0.12422837255001412, // 5535.42 ÷ 44558.42 = 0.12422837255001412
         netPerformanceWithCurrencyEffect: 5535.42,
         netWorth: 50098.3, // 1 * 50098.3 = 50098.3
         totalAccountBalance: 0,
diff --git a/apps/api/src/app/portfolio/calculator/roai/portfolio-calculator-btcusd.spec.ts b/apps/api/src/app/portfolio/calculator/roai/portfolio-calculator-btcusd.spec.ts
index 71820cde4..cf07eff97 100644
--- a/apps/api/src/app/portfolio/calculator/roai/portfolio-calculator-btcusd.spec.ts
+++ b/apps/api/src/app/portfolio/calculator/roai/portfolio-calculator-btcusd.spec.ts
@@ -149,8 +149,8 @@ describe('PortfolioCalculator', () => {
         date: '2021-12-12',
         investmentValueWithCurrencyEffect: 44558.42,
         netPerformance: 5535.42, // 1 * (50098.3 - 44558.42) - 4.46 = 5535.42
-        netPerformanceInPercentage: 0,
-        netPerformanceInPercentageWithCurrencyEffect: 0,
+        netPerformanceInPercentage: 0.12422837255001412, // 5535.42 ÷ 44558.42 = 0.12422837255001412
+        netPerformanceInPercentageWithCurrencyEffect: 0.12422837255001412, // 5535.42 ÷ 44558.42 = 0.12422837255001412
         netPerformanceWithCurrencyEffect: 5535.42, // 1 * (50098.3 - 44558.42) - 4.46 = 5535.42
         netWorth: 50098.3, // 1 * 50098.3 = 50098.3
         totalAccountBalance: 0,
diff --git a/apps/api/src/app/portfolio/calculator/roai/portfolio-calculator-novn-buy-and-sell.spec.ts b/apps/api/src/app/portfolio/calculator/roai/portfolio-calculator-novn-buy-and-sell.spec.ts
index 0854bd20b..3d4760be7 100644
--- a/apps/api/src/app/portfolio/calculator/roai/portfolio-calculator-novn-buy-and-sell.spec.ts
+++ b/apps/api/src/app/portfolio/calculator/roai/portfolio-calculator-novn-buy-and-sell.spec.ts
@@ -153,8 +153,8 @@ describe('PortfolioCalculator', () => {
         date: '2022-03-07',
         investmentValueWithCurrencyEffect: 151.6,
         netPerformance: 24, // 2 * (87.8 - 75.8) = 24
-        netPerformanceInPercentage: 0,
-        netPerformanceInPercentageWithCurrencyEffect: 0,
+        netPerformanceInPercentage: 0.158311345646438, // 24 ÷ 151.6 = 0.158311345646438
+        netPerformanceInPercentageWithCurrencyEffect: 0.158311345646438, // 24 ÷ 151.6 = 0.158311345646438
         netPerformanceWithCurrencyEffect: 24,
         netWorth: 175.6, // 2 * 87.8 = 175.6
         totalAccountBalance: 0,
diff --git a/apps/api/src/app/portfolio/calculator/roai/portfolio-calculator.ts b/apps/api/src/app/portfolio/calculator/roai/portfolio-calculator.ts
index 97b10cae8..d9da465f9 100644
--- a/apps/api/src/app/portfolio/calculator/roai/portfolio-calculator.ts
+++ b/apps/api/src/app/portfolio/calculator/roai/portfolio-calculator.ts
@@ -708,17 +708,23 @@ export class RoaiPortfolioCalculator extends PortfolioCalculator {
           investmentValuesWithCurrencyEffect[order.date] ?? new Big(0)
         ).add(transactionInvestmentWithCurrencyEffect);
 
+        // If duration is effectively zero (first day), use the actual investment as the base.
+        // Otherwise, use the calculated time-weighted average.
         timeWeightedInvestmentValues[order.date] =
-          totalInvestmentDays > 0
+          totalInvestmentDays > Number.EPSILON
             ? sumOfTimeWeightedInvestments.div(totalInvestmentDays)
-            : new Big(0);
+            : totalInvestment.gt(0)
+              ? totalInvestment
+              : new Big(0);
 
         timeWeightedInvestmentValuesWithCurrencyEffect[order.date] =
-          totalInvestmentDays > 0
+          totalInvestmentDays > Number.EPSILON
             ? sumOfTimeWeightedInvestmentsWithCurrencyEffect.div(
                 totalInvestmentDays
               )
-            : new Big(0);
+            : totalInvestmentWithCurrencyEffect.gt(0)
+              ? totalInvestmentWithCurrencyEffect
+              : new Big(0);
       }
 
       if (PortfolioCalculator.ENABLE_LOGGING) {