diff --git a/calculator/calculator.app.js b/calculator/calculator.app.js
index 2767d01..5e7fc12 100644
--- a/calculator/calculator.app.js
+++ b/calculator/calculator.app.js
@@ -37,7 +37,7 @@ var numbers = {
   '6': {grid: [2, 1], globalGrid: [2, 2], trbl: '9-35'},
   '7': {grid: [0, 0], globalGrid: [0, 1], trbl: 'R847'},
   '8': {grid: [1, 0], globalGrid: [1, 1], trbl: 'N957'},
-  '9': {grid: [2, 0], globalGrid: [2, 1], trbl: '%*68'},
+  '9': {grid: [2, 0], globalGrid: [2, 1], trbl: 'p*68'},
   'B': {grid: [0, 3], globalGrid: [0, 4], trbl: '10BB', val: '<-', color: COLORS.SPECIAL},
 };
 
@@ -46,7 +46,7 @@ var operators = {
   '+': {grid: [0, 0], globalGrid: [3, 3], trbl: '-+=3'},
   '-': {grid: [1, 0], globalGrid: [3, 2], trbl: '*-+6'},
   '*': {grid: [0, 1], globalGrid: [3, 1], trbl: '/*-9'},
-  '/': {grid: [1, 1], globalGrid: [3, 0], trbl: '//*%'},
+  '/': {grid: [1, 1], globalGrid: [3, 0], trbl: '//*p'},
   '=': {grid: [1, 2], globalGrid: [3, 4], trbl: '+==.'},
 };
 
@@ -73,8 +73,8 @@ var scientificOperators = {
 var specialsGrid = [2, 2];
 var specials = {
   'R': {grid: [0, 0], globalGrid: [0, 0], trbl: 'RN7R', val: 'AC'},
-  'N': {grid: [1, 0], globalGrid: [1, 0], trbl: 'N%8R', val: '+/-'},
-  '%': {grid: [0, 1], globalGrid: [2, 0], trbl: '%/9N'},
+  'N': {grid: [1, 0], globalGrid: [1, 0], trbl: 'Np8R', val: '+/-'},
+  'p': {grid: [0, 1], globalGrid: [2, 0], trbl: 'p/9N', val: 'Pi'},
   'send': {grid: [1, 1], val: 'send'},
 };
 
@@ -366,15 +366,16 @@ function buttonPress(val) {
       hasPressedNumber = false;
       displayOutput(0);
       break;
-    case '%':
-      if (results != null) {
-        displayOutput(results /= 100);
-        prevExpression = "(" + prevExpression + ")/100";
-      } else if (currNumber != null) {
-        displayOutput(currNumber /= 100);
-        currExpression = "(" + currExpression + ")/100";
+    case 'p':
+      specials.R.val = 'C';
+      if (!swipeEnabled) drawKey('R', specials.R);
+      currNumber = Math.PI;
+      if (hasPressedEquals === 1) {
+        hasPressedEquals = 2;
       }
-      hasPressedNumber = false;
+      hasPressedNumber = currNumber;
+      currExpression = currNumber.toString();
+      displayOutput(currNumber);
       break;
     case 'r':
       if (results != null) {
diff --git a/calculator/test.js b/calculator/test.js
index 5c4a89a..41b9282 100644
--- a/calculator/test.js
+++ b/calculator/test.js
@@ -330,7 +330,6 @@ const unaryOps = {
   'r': { name: 'sqrt', fn: Math.sqrt },
   's': { name: 'x^2', fn: (a) => a * a },
   'i': { name: '1/x', fn: (a) => 1 / a },
-  '%': { name: '%', fn: (a) => a / 100 },
 };
 
 for (const op in unaryOps) {
@@ -501,5 +500,22 @@ test('Negative zero handling', () => {
   checkDisplay(-0);
 });
 
+test('Pi button', () => {
+  press('p');
+  checkDisplay(Math.PI);
+  press('*2=');
+  checkDisplay(Math.PI * 2);
+});
+
+test('Pi replaces current number entry', () => {
+  press('123p');
+  checkDisplay(Math.PI);
+});
+
+test('Operation with Pi', () => {
+  press('5*p=');
+  checkDisplay(5 * Math.PI);
+});
+
 // Run all the defined tests
 runTests();