Uphill / Downhill Shot Correction
The cosine-rule correction for elevated or depressed shots.
How this works
A rangefinder measures the straight-line (slant) distance to the target, but gravity only acts along the true horizontal distance the bullet actually travels through. The cosine rule converts slant range into that effective horizontal distance — the "shorter" number your trajectory should really be calculated against.
Why uphill and downhill behave the same
Since the correction only depends on the angle's cosine, not its sign, a 30° uphill shot and a 30° downhill shot at the same slant distance get the identical correction and the identical point of impact relative to a flat shot at that same distance. Both angled shots hit higher than shooters instinctively expect, which is the classic angle-shooting mistake this calculator is built to prevent.
Frequently asked questions
Do uphill and downhill shots really drop the same amount?
Yes, for the same slant distance and angle — the cosine-rule correction only depends on the angle's cosine, which is identical whether the angle is up or down. Both directions hit higher than the naive slant-range prediction by the same amount.
At what angle does this correction start to matter?
Below about 15 degrees the correction is usually small enough to ignore for typical hunting shots, but steep treestand or mountain shots (30 degrees or more) can meaningfully shift point of impact and are worth correcting for.
Does my rangefinder already do this correction?
Many modern hunting rangefinders have an "angle compensation" or "angle intelligence" mode that applies this same math automatically — check your specific model's manual, and use this calculator to double-check the result if you're unsure.
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