Bicycle tire spokes almost always break at the 90-degree bend where the spoke hooks onto the hub -- it's an inherent weak spot. To order a new spokes, you must have nearly perfect measurement. The only way to accurately measure for new spokes is to remove the broken spokes and use one of them as a template.This makes it easy to gauge the length you need for a replacement. Broken spokes never fall out completely. When you hear that tinkling sound when your spoke breaks, it's a good idea to stop riding your bike and remove it for reference.
Roll the bike so that the broken spoke is facing straight down.
Grab the broken spoke with your fingers and twist it counterclockwise until it comes out of the rim.
Remove the 90-degree broken end if it is still on the rim.
Lay the spoke out on a flat surface, including the broken end if you have it.
Measure from the end of the threads on the threaded end to the point where the spoke makes the 90-degree bend.
Building bicycle wheels from scratch requires training. If your were to try this, all of your spokes, rim, hub and gears would come as a pre-measured kit, or be specified by training manuals or the manufacturers. If your spoke is hopelessly bent, or you lose it. Use a tape measure to measure an existing spoke still on the wheel and then add 1/4-inch.