diff --git a/rest-api/src/controller/rest.controller.ts b/rest-api/src/controller/rest.controller.ts
index e97fcbd..2c262f5 100644
--- a/rest-api/src/controller/rest.controller.ts
+++ b/rest-api/src/controller/rest.controller.ts
@@ -33,6 +33,8 @@ import {
   SwapCalcInfo,
 } from '../service/sdk.service';
 import { httpException } from '../error/errors';
+import Big from 'big.js';
+import { convertIntAmountToFloat } from '../utils/calculation';
 
 type RawTransaction =
   | VersionedTransaction
@@ -172,13 +174,13 @@ export class RestController {
         HttpStatus.BAD_REQUEST,
       );
     }
-    const floatAmount = parseFloat(amount) / 10 ** sourceTokenObj.decimals;
-    if (isNaN(floatAmount)) {
-      throw new HttpException('Invalid amount', HttpStatus.BAD_REQUEST);
-    }
-    const minimumReceiveAmountFloat =
-      parseFloat(minimumReceiveAmount) / 10 ** destinationTokenObj.decimals;
-    if (isNaN(minimumReceiveAmountFloat)) {
+    let minimumReceiveAmountFloat: string;
+    try {
+      minimumReceiveAmountFloat = convertIntAmountToFloat(
+        minimumReceiveAmount,
+        destinationTokenObj.decimals,
+      ).toFixed();
+    } catch (e) {
       throw new HttpException(
         'Invalid minimumReceiveAmount',
         HttpStatus.BAD_REQUEST,
@@ -194,11 +196,11 @@ export class RestController {
       );
     }
     const params = {
-      amount: floatAmount.toString(),
+      amount: convertGt0IntAmountToFloat(amount, sourceTokenObj.decimals),
       destinationToken: destinationTokenObj,
       fromAccountAddress: sender,
       minimumReceiveAmount: minimumReceiveAmount
-        ? minimumReceiveAmountFloat.toString()
+        ? minimumReceiveAmountFloat
         : undefined,
       sourceToken: sourceTokenObj,
       toAccountAddress: recipient,
@@ -360,10 +362,6 @@ export class RestController {
     }
     const feePaymentMethodEnum =
       FeePaymentMethod[feePaymentMethod as keyof typeof FeePaymentMethod];
-    const amountFloat = parseFloat(amount) / 10 ** sourceTokenObj.decimals;
-    if (isNaN(amountFloat) || amountFloat <= 0) {
-      throw new HttpException('Invalid amount', HttpStatus.BAD_REQUEST);
-    }
     if (
       !!solanaTxFeeParams &&
       !Object.keys(SolanaTxFeeParamsMethod).includes(solanaTxFeeParams)
@@ -374,7 +372,7 @@ export class RestController {
       );
     }
     const sendParams = {
-      amount: amountFloat.toString(),
+      amount: convertGt0IntAmountToFloat(amount, sourceTokenObj.decimals),
       destinationToken: destinationTokenObj,
       fromAccountAddress: sender,
       sourceToken: sourceTokenObj,
@@ -833,14 +831,14 @@ export class RestController {
     }
     const messengerEnum = Messenger[messenger as keyof typeof Messenger];
     const feeFloat = relayerFeeInStables
-      ? (
-          parseFloat(relayerFeeInStables) /
-          10 ** sourceTokenObj.decimals
-        ).toString()
+      ? convertIntAmountToFloat(
+          relayerFeeInStables,
+          sourceTokenObj.decimals,
+        ).toFixed()
       : undefined;
     try {
       return await this.sdkService.getAmountToBeReceived(
-        amount,
+        convertGt0IntAmountToFloat(amount, sourceTokenObj.decimals),
         sourceTokenObj,
         destinationTokenObj,
         messengerEnum,
@@ -896,14 +894,14 @@ export class RestController {
     }
     const messengerEnum = Messenger[messenger as keyof typeof Messenger];
     const feeFloat = relayerFeeInStables
-      ? (
-          parseFloat(relayerFeeInStables) /
-          10 ** sourceTokenObj.decimals
-        ).toString()
+      ? convertIntAmountToFloat(
+          relayerFeeInStables,
+          sourceTokenObj.decimals,
+        ).toFixed()
       : undefined;
     try {
       return await this.sdkService.getAmountToSend(
-        amount,
+        convertGt0IntAmountToFloat(amount, destinationTokenObj.decimals),
         sourceTokenObj,
         destinationTokenObj,
         messengerEnum,
@@ -962,7 +960,7 @@ export class RestController {
       );
     }
     const params = {
-      amount: amount.toString(),
+      amount: convertGt0IntAmountToFloat(amount, tokenAddressObj.decimals),
       accountAddress: ownerAddress,
       token: tokenAddressObj,
     };
@@ -1037,7 +1035,7 @@ export class RestController {
       );
     }
     const params = {
-      amount: amount.toString(),
+      amount: convertGt0IntAmountToFloat(amount, tokenAddressObj.decimals),
       accountAddress: ownerAddress,
       token: tokenAddressObj,
     };
@@ -1183,13 +1181,9 @@ export class RestController {
     }
     const feePaymentMethodEnum =
       FeePaymentMethod[feePaymentMethod as keyof typeof FeePaymentMethod];
-    const floatAmount = parseFloat(amount) / 10 ** tokenAddressObj.decimals;
-    if (isNaN(floatAmount) || floatAmount <= 0) {
-      throw new HttpException('Invalid amount', HttpStatus.BAD_REQUEST);
-    }
     try {
       return await this.sdkService.checkAllowance({
-        amount: floatAmount.toString(),
+        amount: convertGt0IntAmountToFloat(amount, tokenAddressObj.decimals),
         owner: ownerAddress,
         token: tokenAddressObj,
         gasFeePaymentMethod: feePaymentMethodEnum,
@@ -1332,7 +1326,7 @@ export class RestController {
     }
     try {
       return await this.sdkService.getAmountToBeDeposited(
-        amount,
+        convertGt0IntAmountToFloat(amount, tokenAddressObj.decimals),
         tokenAddressObj,
       );
     } catch (e) {
@@ -1362,13 +1356,9 @@ export class RestController {
     if (!tokenAddressObj) {
       throw new HttpException('Token not found', HttpStatus.BAD_REQUEST);
     }
-    const floatAmount = parseFloat(amount) / 10 ** tokenAddressObj.decimals;
-    if (isNaN(floatAmount) || floatAmount <= 0) {
-      throw new HttpException('Invalid amount', HttpStatus.BAD_REQUEST);
-    }
     try {
       return await this.sdkService.getAmountToBeWithdrawn(
-        floatAmount.toString(),
+        convertGt0IntAmountToFloat(amount, tokenAddressObj.decimals),
         ownerAddress,
         tokenAddressObj,
       );
@@ -1377,3 +1367,20 @@ export class RestController {
     }
   }
 }
+
+export function convertGt0IntAmountToFloat(
+  amount: string,
+  decimals: number,
+  exceptionMsg: string = 'Invalid amount',
+): string {
+  let amountFloatBig: Big;
+  try {
+    amountFloatBig = convertIntAmountToFloat(amount, decimals);
+  } catch (e) {
+    throw new HttpException(exceptionMsg, HttpStatus.BAD_REQUEST);
+  }
+  if (amountFloatBig.lte(0)) {
+    throw new HttpException(exceptionMsg, HttpStatus.BAD_REQUEST);
+  }
+  return amountFloatBig.toFixed();
+}
diff --git a/rest-api/src/service/sdk.service.ts b/rest-api/src/service/sdk.service.ts
index 374378a..52f3fa1 100644
--- a/rest-api/src/service/sdk.service.ts
+++ b/rest-api/src/service/sdk.service.ts
@@ -269,7 +269,7 @@ export class SDKService {
   }
 
   async getAmountToBeReceived(
-    amount: string,
+    amountFloat: string,
     sourceToken: TokenWithChainDetails,
     destinationToken: TokenWithChainDetails,
     messenger: Messenger,
@@ -281,13 +281,13 @@ export class SDKService {
     }
     try {
       const amountToSendFloat = stableFeeInFloat
-        ? Big(amount)
+        ? Big(amountFloat)
             .minus(stableFeeInFloat)
             .round(sourceToken.decimals)
             .toFixed()
-        : amount;
+        : amountFloat;
       if (Big(amountToSendFloat).lte(0)) {
-        return { amountInFloat: amount, amountReceivedInFloat: '' };
+        return { amountInFloat: amountFloat, amountReceivedInFloat: '' };
       }
       let amountReceived: string;
       if (
@@ -308,16 +308,19 @@ export class SDKService {
           messenger,
         );
       }
-      return { amountInFloat: amount, amountReceivedInFloat: amountReceived };
+      return {
+        amountInFloat: amountFloat,
+        amountReceivedInFloat: amountReceived,
+      };
     } catch (e: any) {
       const errorCode = e.errorCode;
       console.error('errorCode', errorCode);
-      return { amountInFloat: amount, amountReceivedInFloat: '' };
+      return { amountInFloat: amountFloat, amountReceivedInFloat: '' };
     }
   }
 
   async getAmountToSend(
-    amountReceived: string,
+    amountReceivedFloat: string,
     sourceToken: TokenWithChainDetails,
     destinationToken: TokenWithChainDetails,
     messenger?: Messenger,
@@ -329,7 +332,7 @@ export class SDKService {
     }
     let amount;
     try {
-      const roundedAmountReceived = Big(amountReceived)
+      const roundedAmountReceived = Big(amountReceivedFloat)
         .round(destinationToken.decimals)
         .toFixed();
       if (
@@ -353,7 +356,7 @@ export class SDKService {
     } catch (e: any) {
       const errorCode = e.errorCode;
       console.error('errorCode', errorCode);
-      return { amountInFloat: '', amountReceivedInFloat: amountReceived };
+      return { amountInFloat: '', amountReceivedInFloat: amountReceivedFloat };
     }
     const amountInFloat = stableFeeInFloat
       ? Big(amount).plus(stableFeeInFloat)
@@ -362,7 +365,7 @@ export class SDKService {
       amountInFloat: amountInFloat
         .round(sourceToken.decimals, Big.roundUp)
         .toFixed(),
-      amountReceivedInFloat: amountReceived,
+      amountReceivedInFloat: amountReceivedFloat,
     };
   }
 
diff --git a/rest-api/src/utils/calculation.ts b/rest-api/src/utils/calculation.ts
new file mode 100644
index 0000000..48a2d50
--- /dev/null
+++ b/rest-api/src/utils/calculation.ts
@@ -0,0 +1,16 @@
+import { Big, BigSource } from 'big.js';
+
+export function convertIntAmountToFloat(
+  amountInt: BigSource,
+  decimals: number,
+): Big {
+  const amountValue = Big(amountInt);
+  if (amountValue.eq(0)) {
+    return Big(0);
+  }
+  return Big(amountValue).div(toPowBase10(decimals));
+}
+
+export function toPowBase10(decimals: number): Big {
+  return Big(10).pow(decimals);
+}