diff --git a/components/marketplace/buy-fractional-order-form.tsx b/components/marketplace/buy-fractional-order-form.tsx
index 75b9da72..f6f84384 100644
--- a/components/marketplace/buy-fractional-order-form.tsx
+++ b/components/marketplace/buy-fractional-order-form.tsx
@@ -19,12 +19,15 @@ import {
   getCurrencyByAddress,
   getPricePerPercent,
   getPricePerUnit,
-  getTotalPriceFromPercentage,
 } from "@/marketplace/utils";
 import z from "zod";
 import { zodResolver } from "@hookform/resolvers/zod";
 import { parseUnits } from "viem";
 import { calculateBigIntPercentage } from "@/lib/calculateBigIntPercentage";
+import {
+  DEFAULT_NUM_FRACTIONS,
+  DEFAULT_NUM_FRACTIONS_DECIMALS,
+} from "@/configs/hypercerts";
 
 const formSchema = z
   .object({
@@ -83,13 +86,17 @@ export const BuyFractionalOrderForm = ({
   const getUnitsToBuy = (percentageAmount: string) => {
     try {
       const hypercertUnits = BigInt(hypercert.units || 0);
-      const percentageAsBigInt = BigInt(Number(percentageAmount) * 100);
+      const percentageAsBigInt = parseUnits(
+        percentageAmount,
+        DEFAULT_NUM_FRACTIONS_DECIMALS,
+      );
       const unitsToBuy =
-        (hypercertUnits * percentageAsBigInt) / BigInt(100 * 100);
-      return unitsToBuy.toString();
+        (hypercertUnits * percentageAsBigInt) /
+        (BigInt(100) * DEFAULT_NUM_FRACTIONS);
+      return unitsToBuy < BigInt(0) ? BigInt(0) : unitsToBuy;
     } catch (e) {
       console.error(e);
-      return "0";
+      return BigInt(0);
     }
   };
 
@@ -153,12 +160,15 @@ export const BuyFractionalOrderForm = ({
   const percentageAmount = form.watch("percentageAmount");
   const pricePerPercent = form.watch("pricePerPercent");
 
+  const unitsToBuy = getUnitsToBuy(percentageAmount);
+  const pricePerUnit = getPricePerUnit(
+    pricePerPercent,
+    BigInt(hypercert.units || 0),
+  );
+
   const totalPrice = formatPrice(
     order.chainId,
-    getTotalPriceFromPercentage(
-      BigInt(pricePerPercent),
-      Number(percentageAmount),
-    ),
+    unitsToBuy * pricePerUnit,
     currency.address,
     true,
   );
@@ -169,10 +179,7 @@ export const BuyFractionalOrderForm = ({
     currency.address,
   );
 
-  const unitsToBuy =
-    BigInt(getUnitsToBuy(percentageAmount)) > BigInt(0)
-      ? getUnitsToBuy(percentageAmount)
-      : "0";
+  const disabled = !form.formState.isValid || unitsToBuy === BigInt(0);
 
   return (
     <Form {...form}>
@@ -189,7 +196,7 @@ export const BuyFractionalOrderForm = ({
             <div className="text-sm text-slate-500">
               You will buy{" "}
               <b>
-                <FormattedUnits>{unitsToBuy}</FormattedUnits>
+                <FormattedUnits>{unitsToBuy.toString()}</FormattedUnits>
               </b>{" "}
               units , for a total of <b>{totalPrice}</b>. (min:{" "}
               {minPercentageAmount}%, max: {maxPercentageAmount}%)
@@ -238,6 +245,7 @@ export const BuyFractionalOrderForm = ({
         variant={"outline"}
         type="button"
         onClick={form.handleSubmit(onSubmit)}
+        disabled={disabled}
       >
         Execute order
       </Button>
diff --git a/configs/hypercerts.ts b/configs/hypercerts.ts
index 9f2eb0db..a95edecf 100644
--- a/configs/hypercerts.ts
+++ b/configs/hypercerts.ts
@@ -8,6 +8,10 @@ const HYPERCERT_API_URL =
 export const HYPERCERTS_API_URL_REST = `${HYPERCERT_API_URL}/v1`;
 export const HYPERCERTS_API_URL_GRAPH = `${HYPERCERT_API_URL}/v1/graphql`;
 
-export const DEFAULT_NUM_FRACTIONS = parseUnits("1", 8);
+export const DEFAULT_NUM_FRACTIONS_DECIMALS = 8;
+export const DEFAULT_NUM_FRACTIONS = parseUnits(
+  "1",
+  DEFAULT_NUM_FRACTIONS_DECIMALS,
+);
 
 export const DEFAULT_DISPLAY_CURRENCY = "usd";
diff --git a/marketplace/hooks.tsx b/marketplace/hooks.tsx
index 0c1a207d..0219bbb8 100644
--- a/marketplace/hooks.tsx
+++ b/marketplace/hooks.tsx
@@ -414,7 +414,7 @@ export const useBuyFractionalMakerAsk = () => {
       totalUnitsInHypercert,
     }: {
       order: MarketplaceOrder;
-      unitAmount: string;
+      unitAmount: bigint;
       pricePerUnit: string;
       hypercertName?: string | null;
       totalUnitsInHypercert?: bigint;
@@ -473,7 +473,7 @@ export const useBuyFractionalMakerAsk = () => {
         takerOrder = hypercertExchangeClient.createFractionalSaleTakerBid(
           order,
           address,
-          unitAmount,
+          unitAmount.toString(),
           pricePerUnit,
         );
       } catch (e) {
@@ -492,7 +492,7 @@ export const useBuyFractionalMakerAsk = () => {
         );
       }
 
-      const totalPrice = BigInt(order.price) * BigInt(unitAmount);
+      const totalPrice = BigInt(order.price) * unitAmount;
       try {
         await setStep("ERC20");
         if (currency.address !== zeroAddress) {
@@ -566,11 +566,7 @@ export const useBuyFractionalMakerAsk = () => {
             <span>
               Congratulations, you successfully bought{" "}
               <b>
-                {calculateBigIntPercentage(
-                  BigInt(unitAmount),
-                  totalUnitsInHypercert,
-                )}
-                %
+                {calculateBigIntPercentage(unitAmount, totalUnitsInHypercert)}%
               </b>{" "}
               of <b>{hypercertName}</b>.
             </span>
diff --git a/marketplace/utils.ts b/marketplace/utils.ts
index be0f7d69..dd65d08f 100644
--- a/marketplace/utils.ts
+++ b/marketplace/utils.ts
@@ -144,19 +144,3 @@ export const isTokenDividableBy = (
     (parseUnits(denominator || "1", currency.decimals) || BigInt(1));
   return remainder === BigInt(0);
 };
-
-export const getTotalPriceFromPercentage = (
-  pricePerPercent: bigint,
-  percentageAmount: number,
-) => {
-  if (percentageAmount < 0 || percentageAmount > 100) {
-    throw new Error("Percentage amount must be between 0 and 100");
-  }
-
-  const precision = 10 ** 16;
-
-  return (
-    (pricePerPercent * BigInt(Math.round(percentageAmount * precision))) /
-    BigInt(precision)
-  );
-};
diff --git a/test/marketplace/utils.test.ts b/test/marketplace/utils.test.ts
index 545df969..280ba11b 100644
--- a/test/marketplace/utils.test.ts
+++ b/test/marketplace/utils.test.ts
@@ -1,10 +1,6 @@
 import { describe, it, expect } from "vitest";
 
-import {
-  getPricePerPercent,
-  getPricePerUnit,
-  getTotalPriceFromPercentage,
-} from "@/marketplace/utils";
+import { getPricePerPercent, getPricePerUnit } from "@/marketplace/utils";
 import { currenciesByNetwork } from "@hypercerts-org/marketplace-sdk";
 import { sepolia } from "viem/chains";
 
@@ -42,23 +38,4 @@ describe("utils", () => {
       // expect(getMinimumPrice("1", chainId, usdc.address)).to.eq(1n);
     });
   });
-
-  describe("getTotalPriceFromPercentage", () => {
-    it("should return the total price from percentage", () => {
-      expect(getTotalPriceFromPercentage(BigInt(1), 100)).to.eq(BigInt(100));
-      expect(() => getTotalPriceFromPercentage(BigInt(1), 200)).toThrowError();
-
-      expect(getTotalPriceFromPercentage(BigInt(1), 10)).to.eq(BigInt(10));
-      expect(getTotalPriceFromPercentage(BigInt(100), 0.1)).to.eq(BigInt(10));
-      expect(getTotalPriceFromPercentage(BigInt(10 ** 6), 0.00001)).to.eq(
-        BigInt(10),
-      );
-      expect(
-        getTotalPriceFromPercentage(BigInt(10 ** 12), 0.00000000001),
-      ).to.eq(BigInt(10));
-      expect(
-        getTotalPriceFromPercentage(BigInt(10 ** 16), 0.000000000000001),
-      ).to.eq(BigInt(10));
-    });
-  });
 });