diff --git a/librustzcash-wrapper/src/lib.rs b/librustzcash-wrapper/src/lib.rs
index bc234f5..7397401 100644
--- a/librustzcash-wrapper/src/lib.rs
+++ b/librustzcash-wrapper/src/lib.rs
@@ -1643,6 +1643,7 @@ pub extern "C" fn rust_wrapper_create_transaction(
     sapoutput_len: usize,
     net: bool,
     bl_height: u32,
+    build: bool,
     out: *mut u8,
     out_len: &mut usize){
     let sap_wit_in: Vec<u8> = marshall_from_haskell_var(sap_wit, sap_wit_len, RW);
@@ -1794,71 +1795,89 @@ pub extern "C" fn rust_wrapper_create_transaction(
             }
         }
     }
-    let spend_params_in: Vec<u8> = marshall_from_haskell_var(sapspend, sapspend_len, RW);
-    let spend_params_reader = Cursor::new(spend_params_in);
-    let spend_prover = SpendParameters::read(spend_params_reader, false).unwrap();
-    let output_params_in: Vec<u8> = marshall_from_haskell_var(sapoutput, sapoutput_len, RW);
-    let output_params_reader = Cursor::new(output_params_in);
-    let output_prover = OutputParameters::read(output_params_reader, false).unwrap();
-    let result = if net {
-        main_builder.build(OsRng, &spend_prover, &output_prover, &FeeRule::standard())
-    } else {
-        test_builder.build(OsRng, &spend_prover, &output_prover, &FeeRule::standard())
-    };
-    match result {
-        Ok(r) => {
-            let mut out_bytes: Vec<u8> = Vec::new();
-            let _t = r.transaction().write_v5(&mut out_bytes);
-            let h = Hhex {bytes: out_bytes};
-            marshall_to_haskell_var(&h, out, out_len, RW);
-        },
-        Err(e) => {
-            match e {
-                Error::InsufficientFunds(y) => {
-                    let x = Hhex {bytes: vec![0]};
-                    marshall_to_haskell_var(&x, out, out_len, RW);
-                },
-                Error::ChangeRequired(y1) => {
-                    let x = Hhex {bytes: vec![1]};
-                    marshall_to_haskell_var(&x, out, out_len, RW);
-                },
-                Error::Fee(_y2) => {
-                    let x = Hhex {bytes: vec![2]};
-                    marshall_to_haskell_var(&x, out, out_len, RW);
-                },
-                Error::Balance(y3) => {
-                    let x = Hhex {bytes: vec![3]};
-                    marshall_to_haskell_var(&x, out, out_len, RW);
-                },
-                Error::TransparentBuild(y4) => {
-                    let x = Hhex {bytes: vec![4]};
-                    marshall_to_haskell_var(&x, out, out_len, RW);
-                },
-                Error::SaplingBuild(y5) => {
-                    let x = Hhex {bytes: vec![5]};
-                    marshall_to_haskell_var(&x, out, out_len, RW);
-                },
-                Error::OrchardBuild(y7) => {
-                    let x = Hhex {bytes: vec![6]};
-                    marshall_to_haskell_var(&x, out, out_len, RW);
-                },
-                Error::OrchardSpend(y8) => {
-                    let x = Hhex {bytes: vec![7]};
-                    marshall_to_haskell_var(&x, out, out_len, RW);
-                },
-                Error::OrchardRecipient(y9) => {
-                    let x = Hhex {bytes: vec![8]};
-                    marshall_to_haskell_var(&x, out, out_len, RW);
-                },
-                Error::SaplingBuilderNotAvailable => {
-                    let x = Hhex {bytes: vec![9]};
-                    marshall_to_haskell_var(&x, out, out_len, RW);
-                },
-                Error::OrchardBuilderNotAvailable => {
-                    let x = Hhex {bytes: vec![10]};
-                    marshall_to_haskell_var(&x, out, out_len, RW);
+    if build {
+        let spend_params_in: Vec<u8> = marshall_from_haskell_var(sapspend, sapspend_len, RW);
+        let spend_params_reader = Cursor::new(spend_params_in);
+        let spend_prover = SpendParameters::read(spend_params_reader, false).unwrap();
+        let output_params_in: Vec<u8> = marshall_from_haskell_var(sapoutput, sapoutput_len, RW);
+        let output_params_reader = Cursor::new(output_params_in);
+        let output_prover = OutputParameters::read(output_params_reader, false).unwrap();
+        let result = if net {
+            main_builder.build(OsRng, &spend_prover, &output_prover, &FeeRule::standard())
+        } else {
+            test_builder.build(OsRng, &spend_prover, &output_prover, &FeeRule::standard())
+        };
+        match result {
+            Ok(r) => {
+                let mut out_bytes: Vec<u8> = Vec::new();
+                let _t = r.transaction().write_v5(&mut out_bytes);
+                let h = Hhex {bytes: out_bytes};
+                marshall_to_haskell_var(&h, out, out_len, RW);
+            },
+            Err(e) => {
+                match e {
+                    Error::InsufficientFunds(y) => {
+                        let x = Hhex {bytes: vec![0]};
+                        marshall_to_haskell_var(&x, out, out_len, RW);
+                    },
+                    Error::ChangeRequired(y1) => {
+                        let x = Hhex {bytes: vec![1]};
+                        marshall_to_haskell_var(&x, out, out_len, RW);
+                    },
+                    Error::Fee(_y2) => {
+                        let x = Hhex {bytes: vec![2]};
+                        marshall_to_haskell_var(&x, out, out_len, RW);
+                    },
+                    Error::Balance(y3) => {
+                        let x = Hhex {bytes: vec![3]};
+                        marshall_to_haskell_var(&x, out, out_len, RW);
+                    },
+                    Error::TransparentBuild(y4) => {
+                        let x = Hhex {bytes: vec![4]};
+                        marshall_to_haskell_var(&x, out, out_len, RW);
+                    },
+                    Error::SaplingBuild(y5) => {
+                        let x = Hhex {bytes: vec![5]};
+                        marshall_to_haskell_var(&x, out, out_len, RW);
+                    },
+                    Error::OrchardBuild(y7) => {
+                        let x = Hhex {bytes: vec![6]};
+                        marshall_to_haskell_var(&x, out, out_len, RW);
+                    },
+                    Error::OrchardSpend(y8) => {
+                        let x = Hhex {bytes: vec![7]};
+                        marshall_to_haskell_var(&x, out, out_len, RW);
+                    },
+                    Error::OrchardRecipient(y9) => {
+                        let x = Hhex {bytes: vec![8]};
+                        marshall_to_haskell_var(&x, out, out_len, RW);
+                    },
+                    Error::SaplingBuilderNotAvailable => {
+                        let x = Hhex {bytes: vec![9]};
+                        marshall_to_haskell_var(&x, out, out_len, RW);
+                    },
+                    Error::OrchardBuilderNotAvailable => {
+                        let x = Hhex {bytes: vec![10]};
+                        marshall_to_haskell_var(&x, out, out_len, RW);
+                    }
                 }
             }
         }
+    } else {
+        let result = if net {
+            main_builder.get_fee(&FeeRule::standard())
+        } else {
+            test_builder.get_fee(&FeeRule::standard())
+        };
+        match result {
+            Ok(r) => {
+                let x = Hhex {bytes: r.to_i64_le_bytes().to_vec()};
+                marshall_to_haskell_var(&x, out, out_len, RW);
+            },
+            Err(e) => {
+                let x = Hhex {bytes: vec![2]};
+                marshall_to_haskell_var(&x, out, out_len, RW);
+            }
+        }
     }
 }
diff --git a/src/C/Zcash.chs b/src/C/Zcash.chs
index 8f27fa2..0f35be4 100644
--- a/src/C/Zcash.chs
+++ b/src/C/Zcash.chs
@@ -287,6 +287,7 @@ import ZcashHaskell.Types
      , toBorshVar* `BS.ByteString'&
      , `Bool'
      , `Word64'
+     , `Bool'
      , getVarBuffer `Buffer HexString'&
      }
   -> `()'
diff --git a/src/ZcashHaskell/Utils.hs b/src/ZcashHaskell/Utils.hs
index db001c8..59b38ed 100644
--- a/src/ZcashHaskell/Utils.hs
+++ b/src/ZcashHaskell/Utils.hs
@@ -133,8 +133,9 @@ createTransaction ::
   -> SaplingOutputParams -- ^ the Sapling circuit output parameters
   -> ZcashNet -- ^ the network to be used
   -> Int -- ^ target block height
+  -> Bool -- ^ True to build, False to estimate fee
   -> Either TxError HexString
-createTransaction sapAnchor orchAnchor tSpend sSpend oSpend outgoing sParams oParams znet bh =
+createTransaction sapAnchor orchAnchor tSpend sSpend oSpend outgoing sParams oParams znet bh build =
   if BS.length (hexBytes txResult) > 1
     then Right txResult
     else case head (BS.unpack $ hexBytes txResult) of
@@ -168,3 +169,4 @@ createTransaction sapAnchor orchAnchor tSpend sSpend oSpend outgoing sParams oPa
         (sapOParams oParams)
         (znet == MainNet)
         (fromIntegral bh)
+        build