OneZero Ballistics Calculator

Zero your rifle with one load and know exactly where a second load will hit, without touching your sights. OneZero is a ballistic calculator for 139 cartridges, from .17 HMR to .50 BMG. Use it for supersonic and subsonic .300 Blackout, a match load and a hunting load, or any two rounds you shoot from one zero. SEE THE SHIFT • Pick a zeroed round and a Round 2, and both fly from the same zero. • The headline shows where Round 2 lands at your distance and the hold to correct it: "12.3 in low · Hold U 11.7 MOA". • The solution updates live as you type. No Calculate button. READ DOPE AT ANY RANGE • Drag across the trajectory chart for drop at any yard. The readout stays put when you lift your finger. • Pinch to zoom, and switch between drop and drift. • The dope card lists up, down, left and right corrections for both loads, plus the shift between them, in MOA or MIL. 4,266 FACTORY LOADS BUILT IN • Pick your rifle's cartridge and browse its factory loads, with published ballistic coefficients and muzzle velocities. • Many include bullet length for stability and spin drift, and a G7 ballistic coefficient where the bullet has one. • Search or filter supersonic and subsonic, then tap a load to use it as your zeroed round or Round 2. WIND FROM YOUR COMPASS • Use Current Weather fills in the wind's speed and the direction it blows from. • Tap Target Direction and point your iPhone at the target, and OneZero works out the wind's clock direction. You can still pick it by hand. ON YOUR WRIST • The Apple Watch app shows the elevation and windage holds for both rounds from your iPhone's setup. • Turn the Digital Crown to step through distances 5 yards at a time. • The windage holds follow the watch's compass, so you can face the next target and read the hold. • Today's sunrise and sunset sit beside the clock, and your setup stays on the watch when your phone doesn't. PHYSICS YOU CAN CHECK • Standard G1 and G7 drag tables indexed by Mach number, the same reference data used by established ballistic solvers. • Air density from station pressure, temperature and humidity, with density altitude and speed of sound shown. • Wind from any direction: crosswind drift by the lag-time method, and head and tail winds in the drag. The wind's clock direction is picked by hand or worked out from compass bearings. • Miller stability and spin drift from your cartridge's bullet diameter, bullet length and barrel twist, corrected for muzzle velocity and air density. • Coriolis from your latitude, with its vertical part for the target's direction. MADE FOR THE RANGE • Use Current Weather fills temperature, humidity, pressure, altitude and wind from Apple Weather for your location. • Save rifles and loads as presets and switch between them in a tap. • Share a PDF dope card with both loads, ready to print. • On iPhone Duo, see Setup and the live solution side by side, split at the fold. • Dark mode and full VoiceOver support. Always confirm your dope with live fire before relying on it. Weather data provided by Apple Weather.