diff --git a/boltcard.service b/boltcard.service
index da84124..db82a32 100644
--- a/boltcard.service
+++ b/boltcard.service
@@ -43,7 +43,9 @@ Environment="LN_PORT=10009"
 Environment="LN_TLS_FILE=/home/ubuntu/boltcard/tls.cert"
 Environment="LN_MACAROON_FILE=/home/ubuntu/boltcard/SendPaymentV2.macaroon"
 
-# FEE_LIMIT_SAT is the maximum lightning network fee to be paid
+# The maximum lightning network fee to be paid in percent of the payment amount.
+Environment="FEE_LIMIT_PERCENT=0.5"
+# Acceptable flat fee in sats that can exceed the percentage limit.
 Environment="FEE_LIMIT_SAT=10"
 
 # email
diff --git a/docs/FAQ.md b/docs/FAQ.md
index be5fd93..8289c09 100644
--- a/docs/FAQ.md
+++ b/docs/FAQ.md
@@ -14,7 +14,7 @@ This will give you a new 128 bit random key as a 32 character hex value.
 
 This is due to your payment lightning node not finding a route to the merchant lightning node.  
 It may help to open well funded channels to other well connected nodes.  
-It may also help to increase your maximum network fee in your service variables, **FEE_LIMIT_SAT** .  
+It may also help to increase your maximum network fee in your service variables, **FEE_LIMIT_SAT** / **FEE_LIMIT_PERCENT** .  
 It can be useful to test paying invoices directly from your lightning node.  
 
 > Why do my payments take so long ?  
diff --git a/lightning.go b/lightning.go
index f4274f4..4d74a63 100644
--- a/lightning.go
+++ b/lightning.go
@@ -12,6 +12,7 @@ import (
 	"time"
 	"crypto/sha256"
 
+	decodepay "github.com/fiatjaf/ln-decodepay"
 	lnrpc "github.com/lightningnetwork/lnd/lnrpc"
 	invoicesrpc "github.com/lightningnetwork/lnd/lnrpc/invoicesrpc"
 	routerrpc "github.com/lightningnetwork/lnd/lnrpc/routerrpc"
@@ -216,6 +217,21 @@ func pay_invoice(card_payment_id int, invoice string) {
 		return
 	}
 
+	fee_limit_percent_str := os.Getenv("FEE_LIMIT_PERCENT")
+	fee_limit_percent, err := strconv.ParseFloat(fee_limit_percent_str, 64)
+	if err != nil {
+		log.WithFields(log.Fields{"card_payment_id": card_payment_id}).Warn(err)
+		return
+	}
+
+	bolt11, _ := decodepay.Decodepay(invoice)
+	invoice_msats := bolt11.MSatoshi
+
+	fee_limit_product := int64((fee_limit_percent / 100) * (float64(invoice_msats) / 1000))
+	if fee_limit_product > fee_limit_sat {
+		fee_limit_sat = fee_limit_product
+	}
+
 	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
 	defer cancel()