Calculator Inputs
Example Data Table
| Scenario | Range | Angle | Velocity | BC | Zero | Wind |
|---|---|---|---|---|---|---|
| Flat, moderate wind | 600 m | 0° | 820 mps | 0.47 | 100 m | 10 mph @ 90° |
| Uphill shot | 450 yd | +20° | 2700 fps | 0.38 | 100 yd | 8 mph @ 60° |
| Cold air, heavier bullet | 800 m | 0° | 790 mps | 0.62 | 100 m | 12 mph @ 90° |
Formula Used
1) Equivalent horizontal range
EHR = R · cos(θ)
Where R is line‑of‑sight range and θ is incline angle.
2) Point‑mass motion with drag
adrag = (k · ρ/ρ₀ · v²) / BC
a = −adrag · (v⃗ /|v⃗|) − g · ŷ
This calculator integrates the equations numerically using small time steps.
3) Angular corrections
angle ≈ offset / distance
Converted to MOA and MRAD, then to clicks using your click value.
How to Use This Calculator
- Measure the target distance with your rangefinding binoculars.
- Enter incline angle if shooting uphill or downhill.
- Fill ammo details: velocity, BC, bullet weight, and zero range.
- Add sight height and environmental conditions for better estimates.
- Set wind speed, wind angle, and wind direction if needed.
- Choose your turret unit and click value for click calculations.
- Press Calculate and review drop, drift, and table.
- Use export buttons to save the trajectory for field notes.
Field Guide Article
1) Why rangefinder binoculars matter
Small ranging errors compound quickly. A 3% distance mistake turns 600 m into 582 m or 618 m, shifting predicted drop and wind hold. This calculator keeps the workflow consistent: measure range, add incline, then translate offsets into MOA, MRAD, and clicks.
2) Angle and equivalent horizontal range
Gravity acts vertically, so the key distance is the horizontal component. The tool uses EHR = R·cos(θ). At 30°, cos(30°)=0.866, so a 500 m line‑of‑sight reading behaves like ~433 m for drop. Wind drift still scales with time of flight, so angle influences drift indirectly.
3) Ballistic coefficient and velocity inputs
Ballistic coefficient (BC) summarizes how efficiently a projectile carries speed. Common G1 BC values run roughly 0.15–0.75. Higher BC usually means less deceleration, shorter time of flight, and reduced drift. Enter your muzzle velocity in mps or fps; 2800 fps ≈ 853 mps.
4) Air density and “thin air” effects
Drag depends on air density. Standard density is about 1.225 kg/m³ near sea level. Warm, low‑pressure air often drops density below 1.10 kg/m³, while cold, high‑pressure conditions can exceed 1.30 kg/m³. Lower density reduces drag, increasing downrange velocity and shrinking corrections.
5) Wind, direction, and quick drift intuition
Crosswind component is W·sin(φ). A 10 mph wind at 60° yields 8.66 mph effective crosswind. This calculator estimates drift from crosswind and time of flight. Longer time in the air means more drift, so high‑BC loads typically drift less at the same range.
6) Converting offsets to turret clicks
Angular correction is approximately offset ÷ distance. For reference, 1 MOA subtends ~2.91 cm at 100 m, and 0.1 mrad subtends 1 cm at 100 m. If your turret is 0.25 MOA/click, then 2.0 MOA equals 8 clicks.
7) Using the trajectory table for planning
The step table lets you spot trend changes and build a quick reference card. Use smaller steps (25–50 m/yd) for mid‑range work and larger steps for scouting. Compare time of flight and velocity rows to judge sensitivity to wind and to verify that the trend matches your field notes.
FAQs
1) What is “equivalent horizontal range”?
It is the line‑of‑sight range projected onto the horizontal axis: EHR = R·cos(θ). Drop correlates more strongly with EHR than with the raw line‑of‑sight distance on angled shots.
2) Should I enter station pressure or sea‑level pressure?
Use the pressure that best represents the air where you are shooting. If your weather app shows station pressure, that’s usually ideal. Sea‑level pressure can still work, but may slightly bias density.
3) Why are my real‑world results different?
This is a simplified model. Real outcomes depend on verified drag curves, barrel length, muzzle devices, zero confirmation, spin drift, and local wind layers. Use the calculator for planning, then true it with actual observations.
4) What click value should I use?
Match your optic: common values are 0.25 MOA per click or 0.1 mrad per click. If you are unsure, check your turret markings or the optic manual and enter that number.
5) How does wind angle affect the answer?
Only the crosswind portion causes lateral drift. A headwind or tailwind has near‑zero lateral component, while a full 90° wind is maximum. The tool uses W·sin(φ) to compute that component.
6) Can I use this for archery or air rifles?
You can, but expect larger errors. Slow projectiles are more sensitive to drag details, and BC conventions differ. Use very accurate velocity and range inputs, then validate against real drops and drift at short distances.