Unless your plan is to only fish for Steelhead in the Pacific northwest or salmon in Alaska, two-handed Spey casting is not something you're likely to get into when you first start out fly fishing.
Spey casting rods can be anywhere from 12 feet to 15 feet (and longer), but single-handed fly rods rarely exceed 10 feet. So, realistically, your decision for fly rod length will likely fall somewhere between 7 feet and 10 feet.
The following is a list of ideal rod lengths (in feet and inches), and weights (wt) for particular fly fishing scenarios:
- Typical sized trout in a typical wadable trout stream- 8'6" to 9', 4 to 6 wt
- Small trout in small overgrown mountain streams- 6' to 7'6", 2 to 3 wt
- Large trout, Steelhead, and salmon in mid-sized to large rivers- 9' to 10', 7 to 9 wt
- Czech nymphing (or similar technique) for trout in a mid-sized to large river- 9'6" to 10'6", 4 to 6 wt
- Bonefish on the flats- 9', 8 wt
- Permit or large Striped Bass from a boat- 9', 10 to 11 wt
- Adult Tarpon from a boat- 9', 12 wt
- Smallmouth Bass in a 40' to 50' wide wadable creek with overhanging branches- 7'6" to 8'6", 6 to 8 wt
- Big Largemouth Bass in a lake, fishing from a bass boat- 9', 7 to 9 wt
- Bluegill (and other panfish) from a boat- 9', 4 to 6 wt
- Largemouth or Smallmouth Bass from a kayak- 7'9" to 8'3", 7 to 9 wt
This list is certainly not all-inclusive, and may be a source of debate for some anglers, but should give you a rough idea of what you might need for your particular brand of fly fishing. If you're still a bit unsure, turn to the experts at your local fly shop.
Just remember, under-weighting your rod so you will have to play fish to exhaustion in order to land them is never good for the fish. Responsible catch and release anglers use appropriately sized rods to land fish efficiently and release them quickly.
Above all, have fun selecting and fishing your first fly rod. There's a good chance it won't be your last.
Learn more about details of the sport at a fishing class