A replacement lace can be the right colour and still be frustratingly wrong. Too short, and tying becomes a struggle. Too long, and the loops trail where you do not want them. Before buying, use the existing shoe and lace as a reference.
Measure what already works
Remove an intact lace and lay it straight beside a tape measure without pulling it into a stretch. Measure from end to end, including the tips. Note whether the original length suited your normal lacing pattern or left more spare length than you wanted.
If one lace has broken, the other shoe may provide a better reference than trying to estimate the missing section. Photograph the lacing before removing it if you want to reproduce the same route through the eyelets.
Use eyelet charts as a starting point
Lace suppliers often offer recommendations by eyelet count. Lace Lab’s sizing chart, for instance, pairs lace lengths with eyelet ranges. Such a chart is useful for the footwear it describes, but shoe shape, spacing and lacing style can affect the length you need. Check whether a chart counts pairs or individual holes.
Also compare width and shape. A thick round lace may not pass comfortably through an opening made for a slimmer one. Flat and round laces can feel different when tightened, and elastic replacements introduce another change. Match the intended use rather than choosing by length alone.
Try the new pair at home before relying on them for a long day out. Lace both shoes consistently, check that the tips pass without force and tie a secure bow with manageable ends. Avoid leaving loops long enough to catch or drag.
Keep a short note of the successful length, shape and shoe model. The next time a tip frays, you will have a practical reference instead of another guess based on a product photo. Replacing a small part is easiest when the choice comes from the shoe in front of you.