Density Altitude Correction
At higher elevations, the air is thinner and less dense. This reduces aerodynamic drag on the arrow, meaning it retains more speed over distance and shoots flatter than at sea level. If you're hunting above 3,000–4,000 feet, this can make a noticeable difference at distances over 40 yards.
Density altitude is the elevation at which the air is behaving — accounting not just for your physical elevation but also temperature, barometric pressure, and humidity. It's more accurate than elevation alone. A warm, humid, low-pressure day at 9,000 ft can have a density altitude of 11,000+ ft.
Inputs
- Elevation (ft) — Your physical altitude above sea level. Check your topo map, phone GPS, or Google Earth for your camp or shooting location.
- Temperature (°F) — Ambient temperature at your shooting location. Warmer = less dense air = arrows fly flatter.
- Barometric pressure (inHg) — Enter the sea-level corrected pressure from your weather app (default 29.92). On a high-pressure day the air is denser; on a low-pressure day, thinner. Leave at 29.92 if you don't have a reading.
- Humidity (%) — Relative humidity from your weather app or a portable weather meter. Humid air is slightly less dense than dry air. Leave at 50 if unsure.
How to Use It
- Scroll to the Altitude & Density Correction section on the generator page.
- Enter your hunting elevation, expected temperature, barometric pressure, and humidity.
- The section displays adjusted speed, air density %, density altitude, and pressure altitude.
- Click Generate Tape — the correction is applied automatically to your tape marks.
Tip: If you chronograph your bow at home (low elevation) and hunt at altitude, generate two tapes: one with all values at default (home tape), and one with your hunting conditions (altitude tape). Print both and swap when you arrive at camp.
Portable weather meter: Devices like the Kestrel give you station pressure directly and calculate density altitude on-screen. If you have one, you can verify your density altitude reading matches what Sight Tape Gen shows before generating your tape.
How the Calculation Works
Your sea-level barometric reading is converted to station pressure using your elevation and temperature via the standard barometric formula. Humidity is factored in using the virtual temperature method — moist air is less dense than dry air at the same temperature and pressure. From station pressure and virtual temperature, we calculate both pressure altitude and density altitude using the standard atmosphere model (ISA). The final density ratio drives the arrow speed correction: each 10% drop in air density adds approximately 2.5% effective speed. At a density altitude of 10,000 ft (roughly 72% sea-level density), expect about 7 fps of effective speed gain.