diff --git a/src/core/payments/constants.ts b/src/core/payments/constants.ts
index 6f044cc..023a8f8 100644
--- a/src/core/payments/constants.ts
+++ b/src/core/payments/constants.ts
@@ -51,3 +51,19 @@ export const BUFFER_DENOMINATOR = 10n
  */
 export const STORAGE_SCALE_MAX = 10_000_000
 export const STORAGE_SCALE_MAX_BI = BigInt(STORAGE_SCALE_MAX)
+
+/** PDP Leaf Size - the payment rate is based on `rawSize` bytes rounded up to the next multiple of 32.
+ *
+ * @see - https://github.com/FilOzone/synapse-sdk/issues/339#issue-3539254596
+ */
+export const PDP_LEAF_SIZE = 32
+
+/**
+ * Pad raw size to the next multiple of 32 bytes
+ *
+ * @param rawSizeBytes - The actual size in bytes
+ * @returns Padded size (next multiple of 32)
+ */
+export function padSizeToPDPLeaves(rawSizeBytes: number): number {
+  return Math.ceil(rawSizeBytes / PDP_LEAF_SIZE) * PDP_LEAF_SIZE
+}
diff --git a/src/core/payments/index.ts b/src/core/payments/index.ts
index 2100abc..ecc76d6 100644
--- a/src/core/payments/index.ts
+++ b/src/core/payments/index.ts
@@ -26,6 +26,7 @@ import {
   MAX_LOCKUP_ALLOWANCE,
   MAX_RATE_ALLOWANCE,
   MIN_FIL_FOR_GAS,
+  padSizeToPDPLeaves,
   STORAGE_SCALE_MAX,
   STORAGE_SCALE_MAX_BI,
   USDFC_DECIMALS,
@@ -826,7 +827,8 @@ export function calculateDepositCapacity(
  * @returns Required allowances for the piece
  */
 export function calculateRequiredAllowances(pieceSizeBytes: number, pricePerTiBPerEpoch: bigint): StorageAllowances {
-  const storageTiB = pieceSizeBytes / Number(SIZE_CONSTANTS.TiB)
+  const paddedSizeBytes = padSizeToPDPLeaves(pieceSizeBytes)
+  const storageTiB = paddedSizeBytes / Number(SIZE_CONSTANTS.TiB)
   return calculateStorageAllowances(storageTiB, pricePerTiBPerEpoch)
 }