Free calculators for the things I kept working out on paper.

Off-Grid Solar, Wire Gauge & Inverter Calculator

Five tools on one page. Size an array and battery bank from your daily use, get the angle to set the panels at and find true south without a compass, pick a wire gauge that survives the distance, and size an inverter for the moment the pump starts.

→ Open the off-grid power calculator

Propane Tank Calculator

How long a bottle or a tank lasts at the rate you actually burn it, what that costs a day and a month, and the one nobody warns you about — whether a bottle that size can hand the gas over fast enough in the cold, or whether it frosts over and drops the heater at four in the morning.

→ Open the propane tank calculator

Gestation & Hatch Date Calculator

Due dates and hatch dates for 78 animals, with the husbandry that hangs off them — when to dry a doe off, when to candle, when to stop turning eggs.

→ Open the gestation & hatch date calculator

More coming: rainwater catchment, cistern sizing, feed planning.

These all run in a browser and need no account. If you want the answers kept against the actual animal, tank or array — with the service history and what it all cost — that is HomePlot. Free, in a browser, works with no signal — or on your iPhone from the App Store.