diff --git a/src/components/MobileOffsetOrder.tsx b/src/components/MobileOffsetOrder.tsx
index 22bc21e..03de30b 100644
--- a/src/components/MobileOffsetOrder.tsx
+++ b/src/components/MobileOffsetOrder.tsx
@@ -73,8 +73,13 @@ export function MobileOffsetOrder({ tons, monetaryAmount, onBack }: Props) {
     savedState?.offsetPercentage ?? 100 // Default to 100% or use saved value
   );
 
+  // Calculate price per ton (rounded up)
+  const roundedPricePerTon = portfolio ? Math.ceil(portfolio.pricePerTon || 18) : 18;
+
   // Calculate the actual tons to offset based on percentage
-  const actualOffsetTons = (tons * offsetPercentage) / 100;
+  // If monetaryAmount is provided (custom amount), calculate tons from the monetary amount
+  const baseTons = monetaryAmount ? (monetaryAmount / roundedPricePerTon) : tons;
+  const actualOffsetTons = (baseTons * offsetPercentage) / 100;
 
   // Format tons for display
   const formatTons = (tons: number): string => {
@@ -214,7 +219,6 @@ export function MobileOffsetOrder({ tons, monetaryAmount, onBack }: Props) {
   };
 
   // Calculate offset cost using the portfolio price (rounded UP to match display)
-  const roundedPricePerTon = portfolio ? Math.ceil(portfolio.pricePerTon || 18) : 18;
   const offsetCost = monetaryAmount || (portfolio ? actualOffsetTons * roundedPricePerTon : 0);
 
   const handleInputChange = (field: keyof typeof formData, value: string) => {
diff --git a/src/components/OffsetOrder.tsx b/src/components/OffsetOrder.tsx
index 6368e38..8032af6 100644
--- a/src/components/OffsetOrder.tsx
+++ b/src/components/OffsetOrder.tsx
@@ -77,8 +77,13 @@ export function OffsetOrder({ tons, monetaryAmount, onBack, calculatorType }: Pr
     savedState?.offsetPercentage ?? 100 // Default to 100% or use saved value
   );
 
+  // Calculate price per ton (rounded up)
+  const roundedPricePerTon = portfolio ? Math.ceil(portfolio.pricePerTon || 18) : 18;
+
   // Calculate the actual tons to offset based on percentage
-  const actualOffsetTons = (tons * offsetPercentage) / 100;
+  // If monetaryAmount is provided (custom amount), calculate tons from the monetary amount
+  const baseTons = monetaryAmount ? (monetaryAmount / roundedPricePerTon) : tons;
+  const actualOffsetTons = (baseTons * offsetPercentage) / 100;
 
   // Format tons for display
   const formatTons = (tons: number): string => {
@@ -193,7 +198,6 @@ export function OffsetOrder({ tons, monetaryAmount, onBack, calculatorType }: Pr
   };
 
   // Calculate offset cost using the portfolio price (rounded UP to match display)
-  const roundedPricePerTon = portfolio ? Math.ceil(portfolio.pricePerTon || 18) : 18;
   const offsetCost = monetaryAmount || (portfolio ? actualOffsetTons * roundedPricePerTon : 0);
 
   return (