diff --git a/Calculator/Calculator.xcodeproj/project.pbxproj b/Calculator/Calculator.xcodeproj/project.pbxproj
index 70b7a3f..1368575 100644
--- a/Calculator/Calculator.xcodeproj/project.pbxproj
+++ b/Calculator/Calculator.xcodeproj/project.pbxproj
@@ -8,6 +8,7 @@
 
 /* Begin PBXBuildFile section */
 		C6586B6D1E7EB8B700AE8920 /* CalculatorUITests.swift in Sources */ = {isa = PBXBuildFile; fileRef = C6586B6C1E7EB8B700AE8920 /* CalculatorUITests.swift */; };
+		C6A38E051E91592900064B44 /* Constants.swift in Sources */ = {isa = PBXBuildFile; fileRef = C6A38E041E91592900064B44 /* Constants.swift */; };
 		C6CE27911E7D733D004FCFC3 /* AppDelegate.swift in Sources */ = {isa = PBXBuildFile; fileRef = C6CE27901E7D733D004FCFC3 /* AppDelegate.swift */; };
 		C6CE27931E7D733D004FCFC3 /* ViewController.swift in Sources */ = {isa = PBXBuildFile; fileRef = C6CE27921E7D733D004FCFC3 /* ViewController.swift */; };
 		C6CE27961E7D733D004FCFC3 /* Main.storyboard in Resources */ = {isa = PBXBuildFile; fileRef = C6CE27941E7D733D004FCFC3 /* Main.storyboard */; };
@@ -39,6 +40,7 @@
 		C6586B6A1E7EB8B700AE8920 /* CalculatorUITests.xctest */ = {isa = PBXFileReference; explicitFileType = wrapper.cfbundle; includeInIndex = 0; path = CalculatorUITests.xctest; sourceTree = BUILT_PRODUCTS_DIR; };
 		C6586B6C1E7EB8B700AE8920 /* CalculatorUITests.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = CalculatorUITests.swift; sourceTree = "<group>"; };
 		C6586B6E1E7EB8B700AE8920 /* Info.plist */ = {isa = PBXFileReference; lastKnownFileType = text.plist.xml; path = Info.plist; sourceTree = "<group>"; };
+		C6A38E041E91592900064B44 /* Constants.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = Constants.swift; sourceTree = "<group>"; };
 		C6CE278D1E7D733D004FCFC3 /* Calculator.app */ = {isa = PBXFileReference; explicitFileType = wrapper.application; includeInIndex = 0; path = Calculator.app; sourceTree = BUILT_PRODUCTS_DIR; };
 		C6CE27901E7D733D004FCFC3 /* AppDelegate.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = AppDelegate.swift; sourceTree = "<group>"; };
 		C6CE27921E7D733D004FCFC3 /* ViewController.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ViewController.swift; sourceTree = "<group>"; };
@@ -113,6 +115,7 @@
 				C6CE27921E7D733D004FCFC3 /* ViewController.swift */,
 				C6CE27941E7D733D004FCFC3 /* Main.storyboard */,
 				C6F47CD41E7D969700E92C9E /* CalculatorBrain.swift */,
+				C6A38E041E91592900064B44 /* Constants.swift */,
 				C6CE27B01E7D7391004FCFC3 /* Supporting Files */,
 			);
 			path = Calculator;
@@ -287,6 +290,7 @@
 				C6F47CD51E7D969700E92C9E /* CalculatorBrain.swift in Sources */,
 				C6CE27931E7D733D004FCFC3 /* ViewController.swift in Sources */,
 				C6CE27911E7D733D004FCFC3 /* AppDelegate.swift in Sources */,
+				C6A38E051E91592900064B44 /* Constants.swift in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};
diff --git a/Calculator/Calculator/CalculatorBrain.swift b/Calculator/Calculator/CalculatorBrain.swift
index 9ed5d22..022ebbf 100644
--- a/Calculator/Calculator/CalculatorBrain.swift
+++ b/Calculator/Calculator/CalculatorBrain.swift
@@ -90,7 +90,12 @@ struct CalculatorBrain {
     
     mutating func setOperand(_ operand: Double) {
         accumulator = operand
-        accumulatorString = String(format: "%g", operand)
+
+        let numberFormatter = NumberFormatter()
+        numberFormatter.numberStyle = .decimal
+        numberFormatter.usesGroupingSeparator = false
+        numberFormatter.maximumFractionDigits = Constants.numberOfDigitsAfterDecimalPoint
+        accumulatorString = numberFormatter.string(from: NSNumber(value: operand))
     }
     
     var result: Double? {
diff --git a/Calculator/Calculator/Constants.swift b/Calculator/Calculator/Constants.swift
new file mode 100644
index 0000000..844d315
--- /dev/null
+++ b/Calculator/Calculator/Constants.swift
@@ -0,0 +1,13 @@
+//
+//  Constants.swift
+//  Calculator
+//
+//  Created by Peter Vanhoef on 2/04/17.
+//  Copyright © 2017 Peter Vanhoef. All rights reserved.
+//
+
+import Foundation
+
+struct Constants {
+    static let numberOfDigitsAfterDecimalPoint = 6
+}
diff --git a/Calculator/Calculator/ViewController.swift b/Calculator/Calculator/ViewController.swift
index 3e4a7cd..f0d0243 100644
--- a/Calculator/Calculator/ViewController.swift
+++ b/Calculator/Calculator/ViewController.swift
@@ -33,7 +33,11 @@ class ViewController: UIViewController {
             return Double(display.text!)!
         }
         set {
-            display.text = String(format: "%g", newValue)
+            let numberFormatter = NumberFormatter()
+            numberFormatter.numberStyle = .decimal
+            numberFormatter.usesGroupingSeparator = false
+            numberFormatter.maximumFractionDigits = Constants.numberOfDigitsAfterDecimalPoint
+            display.text = numberFormatter.string(from: NSNumber(value: newValue))
         }
     }
     
diff --git a/Calculator/CalculatorTests/CalculatorBrainTests.swift b/Calculator/CalculatorTests/CalculatorBrainTests.swift
index 7d5a2d1..daca994 100644
--- a/Calculator/CalculatorTests/CalculatorBrainTests.swift
+++ b/Calculator/CalculatorTests/CalculatorBrainTests.swift
@@ -246,7 +246,7 @@ class CalculatorBrainTests: XCTestCase {
         testBrain.performOperation("+")
         testBrain.setOperand(1)
         testBrain.performOperation("=")
-        XCTAssertEqual(testBrain.description, "4.123456 + 1")
+        XCTAssertEqual(testBrain.description, "4.123457 + 1")
         XCTAssertFalse(testBrain.resultIsPending)
         XCTAssertTrue(abs(testBrain.result! - 5.123456) < 0.0001)
     }
diff --git a/Calculator/CalculatorUITests/CalculatorUITests.swift b/Calculator/CalculatorUITests/CalculatorUITests.swift
index 45eca10..2d3a80f 100644
--- a/Calculator/CalculatorUITests/CalculatorUITests.swift
+++ b/Calculator/CalculatorUITests/CalculatorUITests.swift
@@ -433,10 +433,10 @@ class CalculatorUITests: XCTestCase {
         app.buttons["8"].tap()
         app.buttons["9"].tap()
         app.buttons["+"].tap()
-        XCTAssert(app.staticTexts["4.123456 + …"].exists)
+        XCTAssert(app.staticTexts["4.123457 + …"].exists)
         app.buttons["1"].tap()
         app.buttons["="].tap()
-        XCTAssert(app.staticTexts["4.123456 + 1 ="].exists)
-        XCTAssert(app.staticTexts["5.123456"].exists)
+        XCTAssert(app.staticTexts["4.123457 + 1 ="].exists)
+        XCTAssert(app.staticTexts["5.123457"].exists)
     }
 }