I have to replace some spokes and the broken ones don't have the little "head" left but do have the curve leading to this head. To measure the length, do I measure from the end of the spoke to the curve (~258mm) or from the top of the threads to the curve (~252mm)?

Also, 4 spokes have broken. The spokes probably aren't high quality ones, although neither is the bike, but I'm told that good quality, double-butted spokes are a good investment. Should I just replace the broken ones with better spokes or should I do the whole wheel?

Any advice would be greatly appreciated.

Yes, spokes are measured from the inside of the elbow to the end. You don't need the head since the elbow is still there for a starting place.

As for the fix or replace question, that's a matter of details and cost. For example if you do the work yourself, it's cheap enough to get four spokes now, and get this back up and running while you consider a long term plan. OTOH if you have to pay a dealer either way, get prices of the various options and decide.

The big question is whether you're throwing good money after bad, and that may depend somewhat of the circumstances. If the spokes broke because of a single incident (crash, branch stuck in wheel, etc.) then you have no reason to suspect that the rest of the spokes are at the end of their lives. But if they broke one at a time, or you've had previous broken spokes, thenodds are the others are also close to the end, and you don't want to put more than small dollars and some personal time into this.

You measure to the end.
If you've broken 4 spokes, the rest are on the way.

You don't "need" butted spokes, but I'd at least use a name brand spoke.

Is this a front or rear wheel? Rears have 2 different lengths.

So do front wheels if they have disc brakes.

When I broke the fourth spoke on my back wheel I bought a new wheel. For me it was the fourth occasion when I broke a single spoke, if you got a stick in the works and pinged four at once and then stopped riding it almost straight away the remainder of yours may still be good.

Like FB said, if these spokes from from a very specific cause then you are probably going to be fine if you just replace these. If they are breaking because of fatigue it is probably a good idea to replace them all.

I believe in DB spokes being superior when it comes to durability but don't think you cant build a wheel that will last thousands upon thousands of miles with straight gauge spokes. If you have a nice hub/rim, sure splurge and get DB. If you are trying to keep a more inexpensive hub/rim combo going I would just use straight gauge from a quality brand like DT or Wheelsmith.

Not a disc wheel, yes, a rear wheel. No stick or accident but the wheel is only 3yrs old, less than 1,000km on it (bike is older, wheel was replaced more recently).

OK, it seems to me that another wheel replacement is in order.

The bike is a 2002 Norco Bigfoot so not an expensive one. I'll ask that I get better quality spokes such as you suggested.

Thanks All!!

According to bikepedia.com, the bike was originally equipped with Sun Rhyno Lite rims.
That's a pretty stout rim, so it must have had cheap and/or ill tensioned spokes.

Riding on the camp roads, washboard-dirt roads and in "pothole city" here, probably did havoc to the bike. I can't say I really looked after it other than oiling chain, changing brake pads, adjusting cables. I wish I knew more about bike maintenance although the tools for it can be expensive.

I've got a book "Zinn and the art of mountain bike maintenance" by Lennard Zinn. He does another one about road bike maintenance. It's worth its weight in gold.

You don't have to buy a pile of tools at once, just buy them as you need them.