Small, useful apps for hobbyists and makers.

Single-purpose iOS calculators for the exact math your hobby needs — water chemistry, cooking, craft, and off-grid.

No card up front. Nothing ever charges automatically.Try free, then pay once — only if you want to keep it.

Free to try No subscriptions No ads No account Works offline
Reef — aquarium chemistry app
Steam — sauna dose calculator app
Crust — pizza dough calculator app
FrostCold Plunge Care

Chlorine or peroxide dosing for chiller or DIY plunges.

› SoakHot Tub Assistant

Chlorine and bromine dosing math for spas.

› ReefAquarium Chemistry

Calcium, alkalinity and magnesium reef dosing.

› AquascapePlanted Tank Calc

EI, PPS-Pro, PMDD or custom fertilizer dosing.

› PondKoi Chemistry

KH, ammonia and nitrite corrective doses.

› SalineSaltwater Pool Care

Salt, stabilizer and saturation index.

› SplashChlorine Pool Care

FC/CYA-aware targets and shock math.

› CrustPizza Dough Calc

Style-aware dough math and a cold-ferment backtimer.

› PressHard Cider Calc

Acidity and tannin balance, plus YAN nutrient math.

› StripUSDA Jerky Safety

Kill-step temps and cure math, USDA-cited.

› SealHome Canning Safety

Altitude-aware USDA processing times and pressures.

› BathSous Vide Cook & Chill

Time, temp and safe cook-chill-reheat timing.

› CureDehydrate & Store

Drying times, conditioning and safe storage.

› CurdCheese Making Calc

Yield, rennet, culture and brine, with affinage.

› TapDraft Beer & CO₂

CO₂ volumes, line length and pour temperature.

› SalumiCharcuterie & Cure

Cure salt weights, water-activity and weight-loss targets.

› CropHydroponic Calc

Target ppm to salt weights, with EC/pH logging.

› FlushMushroom Cultivation

Substrate hydration, agar and spawn math.

› TurfLawn Care Calc

Nitrogen, seeding and weed-control rates by lawn size.

› FluxGlaze Chemistry

Live UMF and per-oxide limit warnings.

› TraceSoap & Lye Calc

SAP-based lye and water, superfat and cure tracker.

› HideLeathermaker's Calc

Saddle-stitch SPI, thread length and edge amounts.

› TemperKnife Heat Treat

Quench and temper targets by steel type.

› WickCandle Maker's Calc

Wax and fragrance weights, wick sizing and cost.

› GrooveTurntable Setup

Cartridge alignment, tracking force and anti-skate.

› LumenRed Light Calc

J/cm² dosing by device and distance.

› MarkerLongevity Bloodwork

ApoB, Lp(a), hsCRP and HbA1c vs optimal ranges.

› SteamSauna Dose Calc

Temp and time targets by experience level.

› WattSolar for Van & RV

Battery, panel, wire gauge and fuse sizing.

› WellOff-Grid Water Calc

Well drawdown, pump head and UV disinfection dose.

› GarageCar Care & Log

Service intervals, fuel economy and reminders.

›

More guides

Topics we cover in depth on the site — guides, ratios and the math behind them.

Fermentation

Kombucha, sauerkraut and kimchi — salt ratios and SCOBY care.
Home Brewing

Beer for beginners — extract vs all-grain and priming math.
Composting

Composting and worm farming — the carbon-to-nitrogen ratio.
Rainwater Harvesting

Catching rain — collection-rate formula and safe-use limits.
Lawn Care

Fertilizer math — nitrogen rate, seed and lime, every number cited.