# Why doesn't this 2d physics calculation yield the desired jump height?

I found a formula for gravity and jumping in this article: http://error454.com/2013/10/23/platformer-physics-101-and-the-3-fundamental-equations-of-platformers/

I implemented this formula and proceeded to do some test calculations, but they yield incorrect results. I expected the outcome to be 4, but the test resulted in 3.8. What am I doing wrong? How do I get the number 4?

float deltaTime = 1f / 50f;

float maxJumpHeight = 4;
float timeToApex = 0.44f;
float gravity = (2 * maxJumpHeight) / (timeToApex * timeToApex);

float jumpHeight = 4;
float jumpVelocity = (float)Math.Sqrt(2 * gravity * jumpHeight);

float velocity = -jumpVelocity;
float position = 0;

while (velocity < 0)
{
velocity += gravity * deltaTime;
position += velocity * deltaTime;
Console.WriteLine("Position = {0}", position);
}