Prospect Your Yard
Measure your backyard with a 300- to 400-foot tape measure to determine how much room you have for a soccer field.
Multiply the length of your field by 0.625 to get the width of your soccer field. Keep planning and field layout simple by rounding to the nearest whole number.
Clear your yard of any brush. Use a machete and riding mower or rent a brushing mower to get rid of tough grass.
Level your yard by filling in any hollows. Use a half-moon spade to cut a cross directly over the center of a shallow pit. Pull the flaps of the cross up with a spade and fill the hollow with high-grade top dressing. Carefully lay the turf back down and tamp it with the back of a rake before watering it.
Make Right Angles
Drive a screwdriver or stake into the ground at one corner of your soccer field. Tie string to it and walk out the length of your sideline, measuring the string with your tape measure. Tie the end of the string to another screwdriver or stake, pull the string tight and drive the screwdriver or stake into the ground to mark the far corner of your field.
Tie another string to a screwdriver or stake to mark another corner of your field. Walk the string out along the baseline of your field, measuring it with a tape measure. Pull the string tight, tie it to another screwdriver or stake and drive it into the ground to mark another corner of the field.
Use the 30-40-50 right triangle method to make sure the corner of the field is a 90-degree angle. Tie one end of a length of string to a screwdriver or stake. Measure and cut the string to 50 feet. Tie the other end to another screwdriver or stake to make a "long edge" length of string.
Measure 30 feet back from the corner down the sideline string. Drive one end of the 50-foot-long edge piece of string into the ground at the 30-foot measurement. Walk the 50-length of string out into the field toward your baseline to create a right triangle with your newly-formed corner.
Measure 40 feet up your baseline's string from the corner. Adjust the angle of your baseline's string so that the 50-foot length connects to the 40-foot mark on the baseline. Your corner is a perfect right angle when the triangle measures 30 feet down the sideline and 40 feet up the baseline with a 50-foot-long edge spanning across the edge of your field.
Pull all strings tight and straight. Adjust the angles of the entire length of each string until you reach a perfect 30-40-50 right triangle. Remove the 50-foot "long edge" length of string and put it aside.
Lay down your other sideline using a tape measure, string and screwdriver stakes. Reuse the 50-foot "long edge" measuring string to ensure that the new corner is a perfect 90 degrees. Lay down the opposite baseline and repeat the 30-40-50 triangle method on the newly-formed corner.
Make Your Mark
Spray paint your soccer field's boundaries along the strings. Do not let your boundary lines fade away or you'll have to stake, string and measure your field again. Apply fresh spray paint every time you mow your field.
Get a friend to hold the end of your tape measure on the corner of the field. Walk the tape measure out before measuring and marking the middle of each sideline boundary with a dash of spray paint.
Drive a screwdriver or stake with string tied around it into one of the sideline dashes. Walk the string to the other sideline dash, pull it tight and anchor it with another screwdriver or stake. Spray paint the midfield line along the string.
Measure the middle of the midfield line using a tape measure. Spray paint a soccer-ball-size dot into the midfield line for the center spot. Remove the string and screwdrivers or stakes.
Use a tape measure to find the middle of each baseline boundary. Mark the middle with a screwdriver or stake in the ground. Place the center of a soccer goal on this mark on each end of the field.