diff --git a/src/actions/ethereum/SendFormValidationActions.js b/src/actions/ethereum/SendFormValidationActions.js
index f8ddecea..66d787d4 100644
--- a/src/actions/ethereum/SendFormValidationActions.js
+++ b/src/actions/ethereum/SendFormValidationActions.js
@@ -347,7 +347,12 @@ export const calculateFee = (gasPrice: string, gasLimit: string): string => {
 
 export const calculateTotal = (amount: string, gasPrice: string, gasLimit: string): string => {
     try {
-        return new BigNumber(amount).plus(calculateFee(gasPrice, gasLimit)).toFixed();
+        const bAmount = new BigNumber(amount);
+        // BigNumber() returns NaN on non-numeric string
+        if (bAmount.isNaN()) {
+            throw new Error('Amount is not a number');
+        }
+        return bAmount.plus(calculateFee(gasPrice, gasLimit)).toFixed();
     } catch (error) {
         return '0';
     }
diff --git a/src/actions/ripple/SendFormValidationActions.js b/src/actions/ripple/SendFormValidationActions.js
index d4f4c765..6ef5bbca 100644
--- a/src/actions/ripple/SendFormValidationActions.js
+++ b/src/actions/ripple/SendFormValidationActions.js
@@ -300,7 +300,12 @@ export const destinationTagValidation = ($state: State): PayloadAction<State> =>
 
 const calculateTotal = (amount: string, fee: string): string => {
     try {
-        return new BigNumber(amount).plus(fee).toFixed();
+        const bAmount = new BigNumber(amount);
+        // BigNumber() returns NaN on non-numeric string
+        if (bAmount.isNaN()) {
+            throw new Error('Amount is not a number');
+        }
+        return bAmount.plus(fee).toFixed();
     } catch (error) {
         return '0';
     }
diff --git a/src/flowtype/npm/bignumber.js b/src/flowtype/npm/bignumber.js
index fd1a31ef..d7bca1a4 100644
--- a/src/flowtype/npm/bignumber.js
+++ b/src/flowtype/npm/bignumber.js
@@ -37,6 +37,7 @@ declare module 'bignumber.js' {
       isLessThan(n: $npm$big$number$object): boolean;
       lte(n: $npm$big$number$object): boolean;
       isLessThanOrEqualTo(n: $npm$big$number$object): boolean;
+      isNaN(): boolean;
       minus(n: $npm$big$number$object): T_BigNumber;
       mod(n: $npm$big$number$object): T_BigNumber;
       plus(n: $npm$big$number$object): T_BigNumber;
diff --git a/src/utils/formatUtils.js b/src/utils/formatUtils.js
index a273959c..37231d7c 100644
--- a/src/utils/formatUtils.js
+++ b/src/utils/formatUtils.js
@@ -56,7 +56,12 @@ export const hexToString = (hex: string): string => {
 
 export const toDecimalAmount = (amount: string | number, decimals: number): string => {
     try {
-        return new BigNumber(amount).div(10 ** decimals).toString(10);
+        const bAmount = new BigNumber(amount);
+        // BigNumber() returns NaN on non-numeric string
+        if (bAmount.isNaN()) {
+            throw new Error('Amount is not a number');
+        }
+        return bAmount.div(10 ** decimals).toString(10);
     } catch (error) {
         return '0';
     }
@@ -64,7 +69,12 @@ export const toDecimalAmount = (amount: string | number, decimals: number): stri
 
 export const fromDecimalAmount = (amount: string | number, decimals: number): string => {
     try {
-        return new BigNumber(amount).times(10 ** decimals).toString(10);
+        const bAmount = new BigNumber(amount);
+        // BigNumber() returns NaN on non-numeric string
+        if (bAmount.isNaN()) {
+            throw new Error('Amount is not a number');
+        }
+        return bAmount.times(10 ** decimals).toString(10);
     } catch (error) {
         return '0';
     }