diff --git a/example/index.html b/example/index.html
index 4d4115d..1fe4aef 100644
--- a/example/index.html
+++ b/example/index.html
@@ -75,6 +75,10 @@ input{
 			<label for="frontIH">Front Inner Height</label>
 			<input name="frontIH" type="number" value="40" /> mm
 		</div>
+		<div>
+			<label for="fold">Fold Section</label>
+			<input name="fold" type="number" value="10" /> mm
+		</div>
 	</div>
 	<div>
 		<div>
@@ -138,6 +142,7 @@ input{
 		const frontIH = Math.round($('frontIH').value * MM);
 
 		const maxLength = Math.round($('maxLength').value * MM);
+		const fold = Math.round($('fold').value * MM);
 
 		const align = Math.round($('align').value);
 		let parts = Math.round($('parts').value);
@@ -161,6 +166,7 @@ input{
 				frontIW : frontIW,
 				frontOH : frontOH,
 				frontIH : frontIH,
+				fold : fold,
 
 				maxLength : maxLength,
 				parts : parts,
diff --git a/src/bellows.js b/src/bellows.js
index ccad989..106d3ad 100644
--- a/src/bellows.js
+++ b/src/bellows.js
@@ -124,6 +124,8 @@ function bellows (options = {}) {
     let backIH = options.backIH || Math.round(MM * 40)
     let backOH = options.backOH || Math.round(MM * 50)
 
+    let fold = options.fold || (frontOW - frontIW) / 2
+
     let align = options.align || 0 //adjust the alignment (find formula)
 
     let maxLength = options.maxLength || MM * 280
@@ -135,7 +137,6 @@ function bellows (options = {}) {
     let key = (typeof options.key !== 'undefined' && options.key === false) ? false : true
     let over = (typeof options.overlap !== 'undefined' && options.overlap === false) ? false : true
 
-    let fold = (frontOW - frontIW) / 2
     let folds = Math.floor(maxLength / fold)
     let length = folds * fold