Calculators & Tools — The Last Light Survival Guide

🍽️ How Much Food Does Your Group Need?

Add each person in your group to calculate total daily food requirements.

Duration

7 days 30 days 90 days 1 year

Daily Calories (group)—

Daily Protein—

Daily Fat—

Food Weight/Day—

Total for Duration—

Calorie Density Reference

Food	Cal/lb	1 day feeds

Reverse: How Long Does My Supply Last?

Food Item

Pounds on Hand

Days This Feeds Group—

💧 Daily Water Budget

Calculate total daily water requirements for your group, animals, and garden.

People

Climate

Season

Livestock

Horses

Cows

Goats

Pigs

Chickens

Garden (sq ft)

Total Daily (gallons)—

Drinking—

Cooking & Hygiene—

Livestock—

Garden Irrigation—

Roof Catchment Calculator

Formula: roof area (sq ft) × rainfall (inches) × 0.623 = gallons harvested

Roof Area (sq ft)

Rainfall (inches)

Gallons Harvested—

Tank Reserve

Tank Size (gallons)

Days of Reserve—

⚡ Off-Grid Power Calculator

Add your loads and select your climate to size a solar system.

Sun Hours/Day by Climate

Daily Watt-Hours Needed—

Panel Wattage (×1.25 safety)—

Battery Bank (3-day, 12V)—

Charge Controller—

Inverter Size—

📦 Supply Tracker

Track what you have and how long it will last. Data saved to your device.

Overall Readiness—

⬆ Import JSON

🧠 Group Skill Inventory

Rate each member 0–3 per skill. Identifies gaps and single points of failure.

Skill

Critical Gaps (no coverage)—

Single Points of Failure—

Rating: 0=None · 1=Basic · 2=Competent · 3=Expert

🌱 What to Plant This Month

Enter your USDA hardiness zone and current month to get planting guidance.

USDA Zone

Month

🌱 Direct Sow Now

—

🪴 Start Indoors Now

—

🍅 Harvest Now

—

📅 Coming Up (30 days)

—

Full Year Calendar

Crop

🚗 Should You Stay or Go?

Answer each question to get a recommendation. Based on standard emergency management principles.

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🖨️ Printable Decision Card

STAY: No immediate threat + safe for 48+ hrs + supplies adequate
GO NOW: Immediate danger + escape route open
SHELTER & DEFEND: Immediate danger + no escape route
PREPARE TO GO: Growing threat + confirmed destination + group can travel
STAY UNLESS: Threat possible but no confirmed destination or route

📻 Emergency Radio Frequencies

Searchable reference. Add your local repeaters and community frequencies.

Name	Frequency	Type	Notes

Add Custom Entry

💊 Field Pharmacology Guide

⚠️ Emergency use only. This information is for genuine emergencies when no medical professional is available. Normal healthcare should always be used when accessible. Incorrect medication use can cause serious harm or death.

Drug	Treats	Adult Dose	Duration	Cautions	Shelf Life

Drug Interaction Checker

Drug 1

Drug 2

Select two medications to check for interactions.

💉 Antibiotic Dosing Calculator

Weight-based oral antibiotic dosing for adults and children — the calculation the adult-dose table above can't do.

⚠️ Emergency reference only — NOT a prescription. These are standard published estimates and may be wrong for your patient. Confirm against the package insert and a clinician whenever one is reachable. Dosing errors can kill — especially in children. Check for drug allergies first, never exceed the adult maximum, and finish the full course.

Patient weight

Units

Antibiotic

Indication

Dose per administration—

Frequency—

Total per day—

Duration—

Adult reference dose—

How much of each formulation per dose

If you have…	Give per dose

⏱️ Survival Timer & Priorities

The rule of 3s, plus countdown timers for time-critical survival tasks. Beeps when done — keep this tab open.

You can survive roughly…	Without
3 minutes	Air (or in icy water)
3 hours	Shelter in harsh weather
3 days	Water
3 weeks	Food

00:00

Custom minutes

🧭 Celestial Latitude Finder

Find your latitude with no GPS — from the North Star at night, or the sun at noon. Measure angles with a fist at arm's length (≈10°) or an improvised sextant.

Method A — Polaris (Northern Hemisphere, at night)

Your latitude ≈ the angle of Polaris (the North Star) above the northern horizon.

Polaris altitude (° above horizon)

Your latitude—

Method B — Noon Sun

Measure the sun's maximum altitude (at local solar noon, its highest point). Enter the date so we can correct for the sun's tilt.

Noon sun altitude (°)

Date

Sun was toward the…

Sun declination (from date)—

Your latitude—

→ See: Navigation & Maps · bundled book: American Practical Navigator (Bowditch)

🔥 Firewood & Heating Estimator

Roughly how much firewood you need to heat a space. Planning estimate — real use varies with stove, wood, and draughts.

Area to heat (sq ft)

Insulation

Temperature difference inside vs out (°F)

Days

Heat needed—

Seasoned hardwood / day—

Total for period—

Cords (approx)—

Assumes seasoned hardwood (~7,000 BTU/lb usable) at ~60% stove efficiency · 1 cord ≈ 4,000 lb. Softwood: ~⅔ the heat per cord.

🌱 Crop Spacing & Seed Planner

How many plants fit a bed, and how many seeds to sow allowing for germination.

Bed length (ft)

Bed width (ft)

Crop

Spacing—

Plants that fit—

Seeds to sow (with germination margin)—

Approx. yield—

Days to harvest—