diff --git a/common/psbt_internal.c b/common/psbt_internal.c
index 454e824fb..dc329c6ca 100644
--- a/common/psbt_internal.c
+++ b/common/psbt_internal.c
@@ -161,3 +161,32 @@ psbt_to_witnesses(const tal_t *ctx,
 
 	return witnesses;
 }
+
+size_t psbt_input_weight(struct wally_psbt *psbt,
+				size_t in)
+{
+	size_t weight;
+	const struct wally_map_item *redeem_script;
+
+	redeem_script = wally_map_get_integer(&psbt->inputs[in].psbt_fields, /* PSBT_IN_REDEEM_SCRIPT */ 0x04);
+
+	/* txid + txout + sequence */
+	weight = (32 + 4 + 4) * 4;
+	if (redeem_script) {
+		weight +=
+			(redeem_script->value_len +
+				(varint_t) varint_size(redeem_script->value_len)) * 4;
+	} else {
+		/* zero scriptSig length */
+		weight += (varint_t) varint_size(0) * 4;
+	}
+
+	return weight;
+}
+
+size_t psbt_output_weight(struct wally_psbt *psbt,
+				 size_t outnum)
+{
+	return (8 + psbt->outputs[outnum].script_len +
+		varint_size(psbt->outputs[outnum].script_len)) * 4;
+}
diff --git a/common/psbt_internal.h b/common/psbt_internal.h
index 166c7a91f..b3a121b7c 100644
--- a/common/psbt_internal.h
+++ b/common/psbt_internal.h
@@ -33,4 +33,12 @@ psbt_to_witnesses(const tal_t *ctx,
 		  const struct wally_psbt *psbt,
 		  enum tx_role side_to_stack);
 
+/* psbt_input_weight - Calculate the tx weight for input index `in` */
+size_t psbt_input_weight(struct wally_psbt *psbt,
+                                size_t in);
+
+/* psbt_output_weight - Calculate the tx weight for output index `outnum` */
+size_t psbt_output_weight(struct wally_psbt *psbt,
+                          size_t outnum);
+
 #endif /* LIGHTNING_COMMON_PSBT_INTERNAL_H */
diff --git a/openingd/dualopend.c b/openingd/dualopend.c
index 1fa6a3a87..442576cb7 100644
--- a/openingd/dualopend.c
+++ b/openingd/dualopend.c
@@ -593,35 +593,6 @@ static bool is_openers(const struct wally_map *unknowns)
 	return serial_id % 2 == TX_INITIATOR;
 }
 
-static size_t psbt_input_weight(struct wally_psbt *psbt,
-				size_t in)
-{
-	size_t weight;
-	const struct wally_map_item *redeem_script;
-
-	redeem_script = wally_map_get_integer(&psbt->inputs[in].psbt_fields, /* PSBT_IN_REDEEM_SCRIPT */ 0x04);
-
-	/* txid + txout + sequence */
-	weight = (32 + 4 + 4) * 4;
-	if (redeem_script) {
-		weight +=
-			(redeem_script->value_len +
-				(varint_t) varint_size(redeem_script->value_len)) * 4;
-	} else {
-		/* zero scriptSig length */
-		weight += (varint_t) varint_size(0) * 4;
-	}
-
-	return weight;
-}
-
-static size_t psbt_output_weight(struct wally_psbt *psbt,
-				 size_t outnum)
-{
-	return (8 + psbt->outputs[outnum].script_len +
-		varint_size(psbt->outputs[outnum].script_len)) * 4;
-}
-
 static bool find_txout(struct wally_psbt *psbt, const u8 *wscript, u32 *funding_txout)
 {
 	for (size_t i = 0; i < psbt->num_outputs; i++) {