That's about what you need, ensure that they're long enough if they're led to the cockpit though. When replacing mine this year, I bought a few meters extra, enabling me to cut off a piece so that the point resting on the sheaves can be moved (it can be end-for-ended the first years). Check your sheaves while you're at it, they might have scratches that can ruin your new halyards in minutes. Use emery cloth to polish them if they need it. You could also just measure the old ones - Tie a small pilot
line to the original halyard, and then pull it through the mast. It’s also easier to rethread the new ones this way – that is by using a pilot
line instead of the original halyard.