The gravitational strength at ground level is approximately 9.81 meters per second squared (m/s²). This is also known as the acceleration due to gravity.

However, there are a few things to consider:

* It's an approximation: 9.81 m/s² is an average value. The actual gravitational acceleration varies slightly depending on your location on Earth due to factors like altitude, latitude, and the density of the Earth's crust.

* It's a measure of acceleration: The value 9.81 m/s² represents the rate at which an object accelerates towards the Earth's center due to gravity.

* It's not a force: The gravitational strength is often confused with the force of gravity. The force of gravity on an object is calculated by multiplying the object's mass by the gravitational acceleration: Force = mass × acceleration.

Therefore, the gravitational strength at ground level is a measure of the acceleration due to gravity, and its value is approximately 9.81 m/s².