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Key to Ballfield Diagrams
Field Dimensions Key | KEY TO FIELD DIAGRAMS (diagrams on pages 10-13)
Red = absolute measurements | Blue = variable / discretionary measurements
A Base Distance: From home to 1st or 3rd, this measurement is taken from the back point (apex) of home plate to the farthest corner of each of 1st or 3rd base along the foul line. Between the bases, the measurement is taken from the outfield side of 1st or 3rd base at the corner by the foul line and extends to the center of 2nd base.
B 1st Base Runner’s Lane Distance: Always 3' to the foul side of the 1st base foul line. It starts exactly halfway down the 1st base line and ends at the back edge of 1st base. It’s marked on the second half of the 1st base line.
C Infield Hypotenuse: Measurement used to ensure the infield is square.
May be measured from the back point (apex) of home plate to the center of 2nd base. Or, from the back corner of 1st base to the back corner of 3rd.
D Infield Arc Radius: From the center of the front edge of the pitching rubber extending toward the outfield grass to the distance recommended.
E Coach’s Box from Foul Line: The distance from the foul edge of the foul line to the line in the coach’s box running parallel to the foul line.
F Coach’s Box Length: The long side of the coach’s box.
G Coach’s Box Width: The short side of the coach’s box.
H Batter’s Box Length: From front to back of the batter’s box.
I Batter’s Box Width: The distance from the inside edge of the batter’s box to the outside edge of the batter’s box.
J Distance to Backstop: The back point of home plate (apex) to any portion of the backstop. Distance listed in the table is the minimum for that league. Distance can be greater than the minimum, but it cannot be any less.
K Minimum Fence Distance: The minimum distance from the apex of home plate, down the right and left field foul lines to the outfield fence.
apex of home plate to the centerfield fence (following field centerline). M Mound Radius: [ BASEBALL ] From the center of the mound outward.
M Mound Radius: [ SOFTBALL ] From the front center of the pitching rubber outward. The circle that is scribed from this radius is what is chalked to define the “Softball Pitcher’s Circle”.
N Pitching Rubber Distance: From the apex of home plate along the centerline to the front center of the pitching rubber.
[ MEASUREMENTS BELOW APPLY TO BASEBALL ONLY ]
O Center of Mound: Measured along the imaginary centerline running from the apex of home plate to the center of 2nd base. Measurement runs from the apex of home plate along the centerline to the distance recommended.
P Mound Height: Height of the mound at the top of the pitching rubber as prescribed by the governing body of the league. (Example: Height of mound should be X" higher than the surface of home plate.)
Q Home Plate Radius: From the back point (apex) of home plate outwards.
R Base Cutout Radius: At 1st and 3rd base, the measurement is taken from the back corner of the base inward to the infield grass. At 2nd base the measurement begins at the center of the base and extends inward to the infield grass.
S 1st and 3rd Baseline Width: Width of the skinned baseline. Typically measured from the foul edge of the foul line. Exact position of the foul line within the baseline is at the groundskeepers discretion. Since the 1980s, the foul line has been kept within 1' of the infield grass. Most base runners run on the foul side of the foul lines, resulting in very little wear on the fair side of the foul lines. Putting majority of the skinned baseline on the foul side of the line puts soil where most of the traffic occurs.
T Infield Grass Edge: Distance from string lines that are run from back of 1st or 3rd to the center of 2nd base, then out to the infield grass edge.
