A broken measuring tape indicates that the spring inside the retraction system may be damaged or disconnected. You may need to clean the internal components to fix it. You need a small screwdriver, masking tape and possibly a new spring.
Open the tape measure
Open the case with a small screwdriver. Hold your finger at the top to prevent the tape from retracting, or use tape. Check to see if the spring is damaged or loose, and look for dirt that may be clogging the mechanism.
Remove the tape
If the inside components aren't dirty or loose, remove the tape from the retraction system while holding the retraction into place. Once the tape is fully stretched, remove the tape from the spring.
Buy a new spring
Replace the spring if it's broken. Tape springs can be purchased from the store where the tape measure was purchased.
Place the tape inside
Connect the tape to the new spring. Place the end portion of the spring into the hole at the starting point of the tape. Use masking tape to hold the mechanism together. Allow the tape to slowly roll back into the mechanism.
Close the case
Test to make sure that the tape functions as normal. Remove the tape that's holding the case. Reapply the cover with the screwdriver.