diff --git a/crates/core/src/rpc/full.rs b/crates/core/src/rpc/full.rs
index 12223186..21ff13eb 100644
--- a/crates/core/src/rpc/full.rs
+++ b/crates/core/src/rpc/full.rs
@@ -45,8 +45,8 @@ use crate::{
     error::{SurfpoolError, SurfpoolResult},
     rpc::utils::{adjust_default_transaction_config, get_default_transaction_config},
     surfnet::{
-        FINALIZATION_SLOT_THRESHOLD, GetTransactionResult, locker::SvmAccessContext,
-        svm::MAX_RECENT_BLOCKHASHES_STANDARD,
+        FINALIZATION_SLOT_THRESHOLD, GetAccountResult, GetTransactionResult,
+        locker::SvmAccessContext, svm::MAX_RECENT_BLOCKHASHES_STANDARD,
     },
     types::{SurfnetTransactionStatus, surfpool_tx_metadata_to_litesvm_tx_metadata},
 };
@@ -1594,6 +1594,7 @@ impl Full for SurfpoolFullRpc {
                             false,
                             &tx_message,
                             None, // No loaded addresses available in error reporting context
+                            None,
                         ))
                         .map_err(|e| {
                             Error::invalid_params(format!(
@@ -1687,6 +1688,53 @@ impl Full for SurfpoolFullRpc {
                 .get_multiple_accounts(&remote_ctx, &transaction_pubkeys, None)
                 .await?;
 
+            let mut seen_accounts = std::collections::HashSet::new();
+            let mut loaded_accounts_data_size: u64 = 0;
+
+            let mut track_accounts_data_size =
+                |account_update: &GetAccountResult| match account_update {
+                    GetAccountResult::FoundAccount(pubkey, account, _) => {
+                        if seen_accounts.insert(*pubkey) {
+                            loaded_accounts_data_size += account.data.len() as u64;
+                        }
+                    }
+                    // According to SIMD 0186, program data is tracked as well as program accounts
+                    GetAccountResult::FoundProgramAccount(
+                        (pubkey, account),
+                        (pd_pubkey, pd_account),
+                    ) => {
+                        if seen_accounts.insert(*pubkey) {
+                            loaded_accounts_data_size += account.data.len() as u64;
+                        }
+                        if let Some(pd) = pd_account {
+                            if seen_accounts.insert(*pd_pubkey) {
+                                loaded_accounts_data_size += pd.data.len() as u64;
+                            }
+                        }
+                    }
+                    GetAccountResult::FoundTokenAccount(
+                        (pubkey, account),
+                        (td_pubkey, td_account),
+                    ) => {
+                        if seen_accounts.insert(*pubkey) {
+                            loaded_accounts_data_size += account.data.len() as u64;
+                        }
+                        if let Some(td) = td_account {
+                            let td_key_in_tx_pubkeys =
+                                transaction_pubkeys.iter().find(|k| **k == *td_pubkey);
+                            // Only count token data accounts that are explicitly loaded by the transaction
+                            if td_key_in_tx_pubkeys.is_some() && seen_accounts.insert(*td_pubkey) {
+                                loaded_accounts_data_size += td.data.len() as u64;
+                            }
+                        }
+                    }
+                    GetAccountResult::None(_) => {}
+                };
+
+            for res in account_updates.iter() {
+                track_accounts_data_size(res);
+            }
+
             svm_locker.write_multiple_account_updates(&account_updates);
 
             // Convert TransactionLoadedAddresses to LoadedAddresses before it gets consumed
@@ -1697,6 +1745,9 @@ impl Full for SurfpoolFullRpc {
                     .get_multiple_accounts(&remote_ctx, &alt_pubkeys, None)
                     .await?
                     .inner;
+                for res in alt_updates.iter() {
+                    track_accounts_data_size(res);
+                }
                 svm_locker.write_multiple_account_updates(&alt_updates);
             }
 
@@ -1751,6 +1802,7 @@ impl Full for SurfpoolFullRpc {
                         config.inner_instructions,
                         &tx_message,
                         loaded_addresses_data.as_ref(),
+                        Some(loaded_accounts_data_size as u32),
                     )
                 }
                 Err(tx_info) => get_simulate_transaction_result(
@@ -1761,6 +1813,7 @@ impl Full for SurfpoolFullRpc {
                     config.inner_instructions,
                     &tx_message,
                     loaded_addresses_data.as_ref(),
+                    Some(loaded_accounts_data_size as u32),
                 ),
             };
 
@@ -2402,6 +2455,7 @@ fn get_simulate_transaction_result(
     include_inner_instructions: bool,
     message: &VersionedMessage,
     loaded_addresses: Option<&solana_message::v0::LoadedAddresses>,
+    loaded_accounts_data_size: Option<u32>,
 ) -> RpcSimulateTransactionResult {
     RpcSimulateTransactionResult {
         accounts,
@@ -2425,7 +2479,7 @@ fn get_simulate_transaction_result(
             Some(metadata.return_data.clone().into())
         },
         units_consumed: Some(metadata.compute_units_consumed),
-        loaded_accounts_data_size: None,
+        loaded_accounts_data_size,
         fee: None,
         pre_balances: None,
         post_balances: None,
diff --git a/crates/core/src/tests/integration.rs b/crates/core/src/tests/integration.rs
index ae3f6ff2..c75e7e0a 100644
--- a/crates/core/src/tests/integration.rs
+++ b/crates/core/src/tests/integration.rs
@@ -609,6 +609,15 @@ async fn test_simulate_add_alt_entries_fetching(test_type: TestType) {
         simulation_res.value.err, None,
         "Unexpected simulation error"
     );
+    assert!(
+        simulation_res.value.loaded_accounts_data_size.is_some(),
+        "Expected loaded_accounts_data_size to be present"
+    );
+    assert_eq!(
+        simulation_res.value.loaded_accounts_data_size.unwrap(),
+        140134,
+        "Incorrect loaded_accounts_data_size value"
+    );
     let simulation_res2 = full_client
         .simulate_transaction(
             data,
@@ -628,6 +637,14 @@ async fn test_simulate_add_alt_entries_fetching(test_type: TestType) {
         simulation_res2.value.err, None,
         "Unexpected simulation error"
     );
+    assert!(
+        simulation_res2.value.loaded_accounts_data_size.is_some(),
+        "Expected loaded_accounts_data_size to be present"
+    );
+    assert!(
+        simulation_res2.value.loaded_accounts_data_size.unwrap() > 0,
+        "Expected loaded_accounts_data_size to be greater than 0"
+    );
 }
 
 #[cfg_attr(feature = "ignore_tests_ci", ignore = "flaky CI tests")]
@@ -722,6 +739,14 @@ async fn test_simulate_transaction_no_signers(test_type: TestType) {
         simulation_res.value.err, None,
         "Unexpected simulation error"
     );
+    assert!(
+        simulation_res.value.loaded_accounts_data_size.is_some(),
+        "Expected loaded_accounts_data_size to be present"
+    );
+    assert!(
+        simulation_res.value.loaded_accounts_data_size.unwrap() > 0,
+        "Expected loaded_accounts_data_size to be greater than 0"
+    );
 }
 
 #[cfg_attr(feature = "ignore_tests_ci", ignore = "flaky CI tests")]