Sleep bedtime calculator
Work out what time to go to bed from your wake-up time, using 90-minute sleep cycles.
Pairs with Sleep Hacks for Busy People.
Open the toolFree tools
Small calculators that run entirely in your browser — nothing is sent anywhere, and nothing is stored. Each one pairs with a book in the series.
Daily water intake calculator
A rough daily water estimate from your body weight and activity level.
Pairs with Hydration Hacks for Busy People.
Open the tool
Grocery budget calculator
Set a monthly grocery target and a per-trip cap from your current spending.
Pairs with Frugal Hacks for Busy Families.
Open the tool