Free
Tools and guides
Free calculators and plain explanations for the problems our apps are built to solve — drilling, compasses, ballistics and Android location testing (the drilling and ballistics apps are coming soon). Every number comes from a published standard or a measurement, and every page says which.
Live universe simulator
The real Solar System on any date, a live sunspot cycle, 8,404 real stars and the Milky Way's measured spiral arms. Share any view.
The Solar System on your birthday
Where every planet was on the day you were born, the Moon’s phase, and when each planet comes back to that spot. Checked against NASA JPL.
Horizontal directional drilling
- Minimum bend radius Calculator — the three separate limits on a bore's curvature, and which one governs.
- Laying out a bore path profile Calculator — depth as the gap between the ground and a path made of arcs and tangents.
- Estimating pullback force Calculator — wall friction, the capstan effect at every bend, fluid drag and buoyancy.
- Drilling fluid volume Calculator — mud per rod and per pass, the top pullback speed for your pump, bentonite bags and returns.
- Reamer size Calculator — 1.5 times the widest point of the pipe or conduit bundle, the 12 in cap over 24 in, picked from your reamers.
Damage prevention
- Potholing and vacuum excavation Calculator — when the standards require an exposure, and the limits that keep it from causing damage.
- Why utility strikes still happen Calculator — what the standards require, and where marked work still goes wrong.
Compass and magnetism
- Magnetic declination calculator Calculator — declination for any place and date from WMM2025, and a compass bearing converted to true north.
- Magnetic interference and phone compasses Calculator — how far a stray field turns a compass, and which checks can catch it.
- How a phone compass finds its heading Calculator — tilt-compensated heading from the accelerometer and magnetometer.
- Magnetic field strength Calculator — total field and dip from WMM2025, and the range a phone magnetometer should read.
- Check a compass against the Sun Calculator — true bearing of a shadow, the Sun, sunrise or sunset, or Polaris, and what is left after declination.
Long-range ballistics
- Rifle Coriolis effect Calculator — horizontal and vertical deflection from latitude, azimuth and time of flight.
- Spin drift Calculator — Miller stability and Litz's drift formula.
- Truing muzzle velocity Calculator — when the chronograph and the target disagree.
- Powder temperature sensitivity Calculator — velocity change per degree from your own chronograph sessions, tested against chronograph noise.
- Chronograph SD and ES Calculator — how far a string’s average and SD can be trusted, how many shots pin them down, and whether two loads really differ.
Android location testing
- Testing a location-dependent Android app — the four ways a chosen position can reach an app under test.
- Simulating movement for geofence and route testing Calculator — testing geofences, distance filters and speed logic with a moving position.
- Change your Tinder location without Passport — how Tinder reads your location on Android, Passport against a one-time spoofer, and the risks.
- Best Pokemon GO spoofer for Android 2026 — spoof without root, hide mock location from the game, $10 once vs monthly subscriptions.
- Change your Bumble location without Travel Mode — Travel Mode shows a badge and costs $40/month. How to appear local anywhere for $10 once.
- Best fake GPS app for Android 2026 — why most fake-GPS apps get caught, how to hide the mock flag, and a comparison of free, one-time, and monthly options.
- Hide mock location on Android — three ways to hide the mock flag without root: patch the app, container mode, or ADB stealth.
- Fake your location on Life360 — how Life360 detects fake GPS, and how to hide it with container mode. No root, $10 once.
- GPS accuracy converter Calculator — CEP, DRMS, 2DRMS, R95, Android’s 68% and the browser’s 95%, and HDOP to metres.