Survival and emergency calculators
Calculators for storms, power cuts and the backcountry — how much water and food to store, how to make water safe, how long a battery will last, how cold it really is and how to navigate without a phone. Every figure comes from an official source such as Ready.gov (FEMA), the US EPA, the CDC, the National Weather Service, Environment Canada or NOAA, named on each page.
Water
Emergency water storage calculatorHow much water to storeHow long will my water last?Days your stored water coversWater purification with bleachDrops of bleach per litre or gallonHow long to boil water to make it safeBoiling time by elevationRainwater collection calculatorWater from rain on a roof
Food
Emergency food calculatorCalories your household needsPower outage food timer: fridge and freezerWhen fridge and freezer food goes bad
Power and energy
Generator wattage calculatorWhat size generator you needGenerator run time and fuel calculatorHours on a tank of fuelBattery run time calculatorHow long a battery powers a deviceHow many phone charges in a power bank?Phone charges per power bankSolar panel output calculatorWatt-hours a day from a panel
Weather and shelter
Wind chill calculatorFeels-like temperature and frostbite riskHeat index calculatorHow hot it feels, with the danger levelHumidex calculatorCanada's heat and humidity indexHow far away is the lightning?Distance from flash to thunder
Navigation
Magnetic declination calculatorCompass north vs true northCoordinate converter: decimal, DMS and UTMDecimal degrees, DMS and UTMDistance and bearing between two pointsFrom one GPS point to anotherHow far is the horizon?Distance to the horizon from a heightHiking time calculator (Naismith's rule)How long a walk or hike takesPace count calculatorMeasure distance by counting stepsHow much daylight is left?Time until sunset and dark
First aid
Emergency planning
Also useful outdoors
Where is the sun now?Its direction and height, liveHow to find northShadow stick, watch and starsDistance between citiesAs the crow flies, with bearingDay and night mapWhere it is light right nowInteractive sky mapStars, constellations and the moonHow long would it take?Walking to the speed of light
For planning and general information. In an emergency, follow the instructions of your local authorities and call your emergency number (911, 112, 999 or 000).