Range Card

Stadiametric Rangefinding

Install this as an app on your device

Game Species · South Africa

Adult shoulder height (at the withers) is the standard reference point for this kind of estimate, sourced from field guides and hunting references. Those published figures are the male animal. Female, calf and young-adult figures aren't independently published for most species — females are scaled by a per-species dimorphism band (equal, modest, clear or strong), and calf/young adult by 55% and 90%, based on typical ungulate growth patterns. Anything marked ~ is a derived estimate, not a measurement — treat it as a starting point and check against your own references.

Athlon Argos BTR Gen 2 · 6-24x50 FFP IR MIL — FFP: mils are true at any magnification

Target Inputs

Target height

Mils subtended

mil

Target spans 4.20 mil — drag the lines to match

±5 mil shown

Mil formula (FFP — no magnification term needed)

Because this reticle is First Focal Plane, the mil subtension you read off the reticle is accurate at any zoom setting — no "true magnification" adjustment required.

Target height in meters

H_m = 1.5 m

→ H = 1.500 m

Solve for distance

D = (H × 1000) ÷ Mils = (1.500 m × 1000) ÷ 4.2

→ D ≈ 357.14 m

Estimated Range

357.1 m

≈ 1172 ft / ≈ 390.6 yd

Reusable formula

D (m) = [ H (m) × 1000 ] ÷ Mils

1 milliradian subtends 1 unit of height at 1000 of that same unit in distance — so keeping H and D in matching units is what makes the formula work. The APMR reticle's hash marks are in 0.5 mil increments, with finer 0.2 mil graduations between 7–9 mil on the stadia lines — estimate your mil reading to the nearest visible graduation for best accuracy.

Binocular Inputs

Magnification

Apparent FOV

Target height

Target fills 1/3.00 of view — drag the lines to match

Fraction of view filled

/ = 0.3333

Fraction exceeds 1 — target is larger than the field of view. Check inputs.

True field of view

True FOV = AFOV ÷ Magnification = 65° ÷ 10

→ True FOV = 6.500°

Angular size of target

θ = f × True FOV = 0.3333 × 6.500°

→ θ = 2.1667°

Convert θ to radians

θ_rad = θ × (π ÷ 180) = 2.1667° × 0.017453

→ θ_rad = 0.03782

Solve for distance

D = H ÷ θ_rad = 1.500 m ÷ 0.03782

→ D ≈ 39.66 m

Estimated Range

39.7 m

≈ 130 ft / ≈ 43.4 yd

Reusable formula

D = H ÷ [ f × (AFOV ÷ M) × 0.017453 ]

AFOV (apparent field of view) is a spec value printed by the binocular manufacturer. Small-angle approximation used in Step 4; accurate within ~0.1% at typical angles.

Experimental — each lens must be calibrated before the range means anything

Camera Rangefinder

Ranges a target from how much of the frame its height fills. Needs camera permission, and this app served over HTTPS.

Lens

Target height

Frozen

Target fills 30.0% of frame height — drag the lines to match

Estimated Range

—

Calibrate this lens to get a range

Lens calibration

The web platform does not report a camera's focal length or field of view, so it has to be measured once per lens. Put an object of known height at a known distance, bracket it with the lines, then calibrate. Stored per lens on this device.

Known height

Known distance (m)

Vertical FOV (°)

Not calibrated.

What this lens reports

Stream & lens properties

—

Zoom is left untouched, since changing it changes the field of view and would invalidate the calibration. Accuracy depends entirely on how carefully the lines are placed — freeze the frame before making the final adjustment.

Video

Live camera preview with a heading-locked mini-map and a tilt readout. Needs camera, location and motion-sensor permission, and this app served over HTTPS. iOS will ask you to confirm the motion-sensor permission.

Lens

Checking calibration…

No recording yet — starts automatically when you turn on Detect objects.

α —

β —

γ —

warming up…

—

The mini-map rotates to keep the direction the back of the phone is pointing at the top — hold the phone upright, camera facing the way you're looking, for the most accurate bearing. Alpha/beta/gamma below are the raw device-orientation sensor angles. "Detect objects" runs a general-purpose on-device detector (~80 everyday classes — people, vehicles, common animals like dogs/horses/cows) entirely on your phone; it does not recognise specific game species. The detector model (~18 MB) downloads once, the first time you turn it on, and is then cached for offline use. Pick which physical camera (lens) to use above — its field of view has to be calibrated once (in the Camera tab) for any distance or bearing math based on this feed to be correct; an uncalibrated lens still previews and detects fine, it just can't measure anything.

Detected objects

Groups the logged detections into candidate sightings of the same object — same class, no more than 5 seconds between readings — and triangulates an estimated position from every reading in the group, the same way a surveyor fixes a point from two or more bearings. Once a distance is known, the same reading's apparent size in frame gives an estimated real-world height too. Sightings of the same class whose fixes land close to each other are then merged together, since that's almost always one real animal or person seen more than once rather than several. The wider the spread of positions you took those readings from (the "arc"), the more reliable the fix; a narrow arc is flagged as low-confidence rather than shown as if it were solid. Needs a calibrated lens above — uncalibrated readings are skipped since there's no way to know their bearing. Distance is measured from your current location, fetched fresh each time.

Press Analyze after logging some detections.

Video Experimental

Records video together with gyro, compass and GPS readings sampled throughout the clip, and saves it into a library kept on this device so you can play it back later — with the same sensor data synced alongside it. Needs camera, location and motion-sensor permission, and this app served over HTTPS. There's no object detection here yet; this tab is just for capturing and reviewing footage with its sensor data intact.

α —

β —

γ —

hdg —

gps —

Not recording. Press Record to capture a clip with synced sensor data.

Recorded clips

Saved on this device only (IndexedDB) — clearing site data or reinstalling the app removes them. Each clip's gyro/compass/GPS log plays back alongside it, synced by timestamp.

Loading…

Scope Adjustment

Enter the table printed on your ammo box below. Velocity drives the calculated drop; energy is shown at your target distance for reference. If you also fill in the manufacturer's trajectory column, those published figures are used directly instead of the estimate — but only while your zero matches the zero that table was measured at.

Bullet velocity, energy & trajectory table

Range (m)

Velocity (m/s)

Energy (J)

Traj. (mm)

Trajectory is the bullet's path relative to your line of sight: positive is above, negative below, and 0 marks the zero range. Leave the muzzle row blank.

Scope & zero settings

Adjustment unit

Click value

mil

Total travel (each way)

mil

Zero distance

Sight height over bore

Target distance

Auto-filled by the "→ Use this range in Ballistics" button on the Scope (MIL) or Binoculars (FOV) tabs.

Time of flight (from velocity table)

t(Zero) and t(Target) — integrated from your velocity table, segment by segment

→ t(zero) = 0.000 s · t(target) = 0.000 s

Gravity drop at each distance

h = ½ × g × t² (g = 9.807 m/s²)

→ h(zero) = 0.000 m · h(target) = 0.000 m

Drop relative to line of sight at target

Drop = (D÷Z)×(h_Z+S) − S − h_D

→ Drop = 0.000 m

Required angular correction

Angle = |Drop| ÷ D → converted to MIL / MOA

→ 0.00 MIL (0.0 MOA)

Clicks to dial

Clicks = Angle ÷ Click value

→ 0 clicks

Dial Direction & Clicks

0 clicks UP

≈ 0.00 MIL · 0.0 MOA

At target distance (reference)

Velocity: — · Energy: —

Reusable formula

Drop = (D/Z)(h_Z+S) − S − h_D | Clicks = (|Drop|/D) ÷ click value

Simplified flat-fire model: assumes level ground (no incline/decline), no wind or spin drift, and linear interpolation between your table rows. Velocity/time is derived directly from your box's own printed data rather than a generic ballistic coefficient, which is a reasonable approximation for typical hunting ranges — for competition-grade precision at long range, a full drag-curve solver will be more accurate.

Quick reference — clicks by distance

Recalculates live from the zero, sight height, and bullet table above. The row matching your current zero is highlighted (0 clicks, by definition).

Range

MIL

MOA

Clicks

Compass

Uses your device's orientation sensor to show heading. Requires this app to be hosted on HTTPS and opened on a phone or tablet — it won't work in this in-chat preview. iOS will ask you to confirm the permission.

0°

warming up…

If the heading seems off, calibrate by moving your phone in a slow figure-8. On iPhone this reads true compass heading; on Android it may read magnetic heading depending on the browser. The reading shown above is smoothed — the badge shows how much it's actually jumping around underneath.

Level

Uses your device's tilt sensor to check cant and tilt — handy for checking rifle cant or leveling a tripod. Works with the phone lying flat or stood upright. Requires this app to be hosted on HTTPS and opened on a phone or tablet.

Pitch

0.0°

Roll

0.0°

warming up…

Green stats mean within 1° of level. Lay the phone flat against the rail/rest for the most accurate cant reading.

Offline Topo Map · Contours

Pan and zoom to your hunting area, then download it for offline use.

Download this area

Saves every tile in the current view so the map still works with no signal. Downloading needs a connection; viewing and pinning never do.

Detail depth

Estimate

—

Saved map data

Checking…

Pins

Contour and hillshade tiles © OpenTopoMap (CC-BY-SA), built from OpenStreetMap data and SRTM elevation. Street tiles © OpenStreetMap contributors. Both are volunteer-funded services — download only the areas you actually need.

Software

Version —

Updates are only checked when you press the button.

Display

Compact mode

Hides the step-by-step working and all explanatory text, leaving only the fields you fill in and the results. Warnings still show.

Sensor filtering

Combats jumpy gyro/compass/GPS readings with a moving-average window and a sampling-rate throttle, each independently tunable per sensor. Turning on "Drop outlier readings" rejects a reading that jumps far outside the recent trend instead of blending it into the average. The same three controls are also one tap away via the ⚙ next to each stability badge on the Video, Compass and Level tabs.

Enable sensor filtering

Turn off to see completely raw, unfiltered readings everywhere below — no smoothing, no outlier rejection. Handy for checking whether a sensor itself is unstable, independent of these settings.

Gyro (tilt)

Window size (samples)

Sampling rate (Hz)

Drop outlier readings

Rejects a gyro reading that jumps far outside the recent trend.

Compass (heading)

Window size (samples)

Sampling rate (Hz)

Drop outlier readings

Rejects a heading that jumps far outside the recent trend.

GPS location

Window size (fixes)

Sampling rate (Hz)

Drop outlier readings

Rejects a GPS fix that jumps far outside the recent trend.

Sensor log

Keeps a rolling 5-minute buffer of the raw, unsmoothed gyro/compass readings (from the Compass, Level and Video tabs) and GPS fixes (from the Video tab's mini-map), entirely on this device — nothing is sent anywhere. Handy for analysing a jumpy reading afterwards. Also logs one row per detected object on the Video tab (class, confidence, its bounding box, frame size, and the active lens's calibrated field of view if it has one) paired with the gyro/compass/GPS reading shown on screen at that same instant — e.g. for working out a bearing to a target from several readings taken at different points.

No samples logged yet — enable Compass, Level or Video to start recording.

Scope reticle

How many mils your reticle covers from the centre crosshair out to the edge of the view. This caps how far the Scope tab can zoom out.

Reticle span ± (mil)

±10 mil · 20 mil total

Scope presets

Turret and zero details for a specific rifle/scope. Applying one fills in the Ballistics tab.

Preset name

Turret unit

Click value

Total travel

Zero (m)

Sight height (cm)

Reticle span ± (mil)

Binocular presets

Magnification and apparent field of view for a pair of binos. Applying one fills in the Binos · FOV tab.

Preset name

Magnification (×)

Apparent FOV (°)

Bullet / load presets

The default velocity and energy table for a load. Applying one fills the Ballistics table. Values normally come off the ammunition manufacturer's data sheet.

Preset name

Range (m)

Velocity (m/s)

Energy (J)

Traj. (mm)

Storage

Checking…

Presets and pins live in this browser's local storage. Clearing site data in your browser settings — or uninstalling the app — removes them.