New bow, box says "350 FPS." You shoot a chronograph and get 298 FPS. You didn't get a lemon — you just ran into the gap between a marketing number and a hunting number. IBO speed is real, standardized, and consistently measured. It's also almost never the speed you'll actually shoot in the field.
What IBO Speed Actually Measures
IBO stands for the International Bowhunting Organization, which set the standard test conditions manufacturers use to rate bow speed. Every IBO-rated bow is tested under identical lab conditions:
- 70 lb draw weight
- 30" draw length
- 350 grain arrow (exactly 5 grains per pound of draw weight)
- No accessories attached — no rest, no sight, no stabilizer, no peep, no D-loop
These conditions exist so bows can be compared apples-to-apples on a spec sheet. They are not remotely close to how most hunters actually shoot a bow. That gap is where the "advertised speed" myth comes from.
Why Your Real Speed Is Almost Always Lower
Every one of the following subtracts speed from the IBO number, and hunters almost always have several of them stacked at once:
| Factor | Typical Speed Impact |
|---|---|
| Draw length shorter than 30" | ~10 fps per inch under 30" |
| Draw weight below 70 lb | ~2 fps per pound under 70 lb |
| Arrow heavier than 5 gr/lb | ~1-2 fps per 3-5 extra grains |
| D-loop and peep sight installed | ~3-6 fps combined |
| Drop-away rest and full accessories | ~2-4 fps |
| Release aid vs. fingers/mechanical variance | ~1-3 fps |
Stack these together and it's common for a hunting-ready bow shooting a realistic hunting arrow to land 40-60 fps below its IBO rating. A bow rated at 340 IBO showing up at 290 fps on a chronograph with a full hunting setup isn't unusual — it's the norm.
Why This Matters for Sighting In
Sight tapes, ballistic apps, and pin gaps are all built from arrow speed. If you build your sight tape using the IBO number printed on the box instead of your actual shooting speed, every distance mark will be wrong — and the error compounds the farther you shoot. A tape built from an inflated speed number will consistently show you hitting low at distance, because your real arrow is slower and drops more than the tape assumes.
The only way to know your real speed is to chronograph your actual hunting arrow, from your actual bow, at your actual draw length and weight — with all accessories attached. Everything else is an estimate.
Estimating Speed Without a Chronograph
Not everyone has access to a chronograph. If you don't, you can estimate your real-world speed by starting from the IBO rating and subtracting for each factor that doesn't match the IBO test conditions: draw length, draw weight, arrow weight, and accessories. It's not as precise as a chronograph reading, but it's far more accurate than sighting in off the number on the box.
Our arrow speed vs. draw weight calculator walks through this estimate using your bow's IBO rating, your actual draw length and weight, and your arrow's true finished weight — giving you a realistic starting speed to build a sight tape from.
Chronograph When You Can
An estimate gets you close. A chronograph reading gets you exact. If you have access to one — many archery pro shops have one on hand — shoot your actual hunting arrow through it before building your final sight tape. It removes every variable in one step and is the single most reliable number you can put into a sight tape calculator.
Build the Tape From Reality, Not the Box
Once you know your real speed — whether chronographed or carefully estimated — that's the number to use, not the IBO rating printed on your bow. Head to SightTapeGen and enter your actual arrow speed to generate a tape that matches how your setup really shoots, not how it performed in a lab with no accessories attached.
The Bottom Line
IBO speed is a standardized lab number, not a prediction of your hunting setup's real speed.
Shorter draw length, lower draw weight, heavier arrows, and accessories all subtract speed — often 40-60 fps combined.
Always sight in from your real speed, chronographed or carefully estimated — never from the number on the box.