What's new

We re-read each calculator's sources on a schedule and change the "last checked" date when we do. Below are all 38 calculators and a log of what has changed.

Changes

• September 30, 2026: Three more Economics Studio tools: a production possibilities frontier and opportunity cost calculator (drag the curve or type a table of points), a GDP deflator calculator for real versus nominal GDP, and a money multiplier calculator with bars for each round of lending.
• September 30, 2026: Three more off-grid tools: a charge controller size calculator (MPPT or PWM, with the cold-weather voltage and the PV fuse), series and parallel wiring for batteries and panels with a diagram that redraws as you type, and a power station runtime calculator that answers whether it will run your fridge.
• September 30, 2026: The off-grid system builder: list your loads and get the battery bank, solar panels, inverter and main cable together, with an energy-flow diagram and a typical-day and winter-day charge chart. The five off-grid calculators now link to it.
• September 30, 2026: Four more Economics Studio tools: price elasticity (midpoint and point method), consumer and producer surplus, tax incidence and deadweight loss, and price ceilings and floors.
• September 30, 2026: The Economics Studio opens with the Supply & Demand Studio: drag the curves, add a tax or subsidy, and see surplus and deadweight loss.
• September 30, 2026: The off-grid power hub opens with five calculators: battery bank size, solar panel size, battery runtime, DC wire size and inverter size.
• September 30, 2026: CalcVisual opens with 21 calculators across aquarium, pool, surf and money.

Aquarium & reef

Pool, hot tub & pond

Off-grid power

Economics Studio

Surf

Travel & money