Outdoors & Survival Tools

Free outdoor, hiking and survival calculators that run entirely in your browser — hiking time (Naismith), firewood cord, backpack weight, water needs, lightning distance, map scale, horizon distance, arrow FOC, paracord length, compass bearing, rope safe working load and tent footprint. Nothing is uploaded.

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Hiking Time Calculator (Naismith's Rule)

Estimate hike time from distance, elevation gain and pace using Naismith's rule, plus a fitness and terrain correction.

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Firewood Cord Calculator

Convert a wood stack's length, height and depth into full cords, face cords, cubic feet, cubic meters and total cost.

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Backpack Weight Calculator

See your loaded pack as a percentage of body weight and check it against the recommended 20–25% limit for hiking.

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Hiking Water Calculator

Estimate how much water to carry on a hike from duration, heat and elevation gain, in liters, ounces and bottles.

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Lightning Distance Calculator (Flash-to-Bang)

Turn the seconds between a lightning flash and the thunder into distance in km and miles, with the 30-30 safety rule.

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Map Scale & Distance Calculator

Convert between map distance, real ground distance and scale ratio (1:N) in any units, including model and drawing scales.

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Distance to Horizon Calculator

Find how far away the horizon is from your eye height, plus the distance at which a distant object rises into view over the curve.

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Arrow FOC Calculator

Compute an arrow's front-of-center (FOC) balance percentage from its length and balance point, with optional kinetic energy and momentum.

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Paracord Length Calculator

Estimate how much paracord to buy for a bracelet, lanyard or project from its finished length and weave, including a waste buffer.

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Compass Declination & Bearing Converter

Convert back bearings, magnetic-to-true bearings with declination, and the initial bearing and distance between two lat/long points.

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Rope Safe Working Load Calculator

Find a rope's safe working load from its breaking strength and safety factor, or estimate it from diameter and material type.

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Tent & Tarp Sizing Calculator

Size a tent footprint tarp slightly smaller than the tent floor, or work out the floor area a number of sleepers actually needs.

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