Free Outdoors & Garden Calculators
This hub gathers calculators for gardeners, homesteaders, hikers, boaters and pet owners. Work out when to start seeds, how much lime a bed needs, how far a leg of a hike is, or how much anchor rode to let out. Everything runs in your browser and nothing is uploaded.
Featured Outdoors & Garden tools
- Seed Starting Date CalculatorTurns your last frost date into indoor start, harden-off and transplant dates.
- Soil pH Lime & Sulfur CalculatorGives lime or sulfur amounts with a season-by-season application schedule.
- Compost Carbon-to-Nitrogen Ratio CalculatorShows the blended carbon-to-nitrogen ratio of your pile and what to add.
- GPS Bearing & Distance CalculatorReturns distance and both true and magnetic bearing between two coordinates.
Planting & Growing
5 toolsDates, spacing and light for vegetables, indoor growing and microgreens.
- Gardeners
Seed Starting Date Calculator
Enter your last frost date, pick your vegetables, and get a personalised planting calendar with indoor start, harden-off, and transplant dates.
- Gardeners
Seed to Harvest Calendar
Add vegetables with sow dates and see germination, transplant, and harvest windows on a Gantt-style chart. Succession planting reminders.
- Gardeners / Market Gardeners
Vegetable Garden Spacing Calculator
Enter raised bed dimensions, add vegetables, and get plant count, a grid layout, and companion planting notes. 25 vegetables.
- Indoor Growers / Home Gardeners
Grow Light PPFD & DLI Calculator
Enter light PPFD and photoperiod to get daily light integral and a verdict for your plant type. Adjust photoperiod to hit target DLI.
- Urban & Microgreens Growers
Microgreens Profit & Break-Even Calculator
Calculate weekly profit, break-even trays, weeks to ROI, and a variety margin ranking for your microgreens growing business.
Soil, Compost & Water
4 toolsCorrect soil pH, balance a compost pile, run a worm bin and check a drip system.
- Backyard & Vegetable Gardeners
Soil pH Lime & Sulfur Calculator
Calculate exactly how much lime or sulfur to add to correct your soil pH, with a season-by-season application schedule based on your soil texture.
- Gardeners / Homesteaders
Compost Carbon-to-Nitrogen Ratio Calculator
Add browns and greens by weight to get the blended carbon-to-nitrogen ratio, a traffic-light verdict, and what to add to balance the pile.
- Vermicomposters & Urban Gardeners
Worm Farm Castings Harvest Calculator
Estimate your monthly worm castings output, first harvest date, and moisture check schedule based on your bin size, worm species, and feeding habits.
- Gardeners / Landscapers
Drip Irrigation Zone Calculator
Add emitters, enter supply line specs, and check whether your water pressure can supply all zones without under-watering.
Landscaping, Fire & Pools
4 toolsBulk material volumes, firewood measures, fire pit setbacks and pool chemistry.
- Landscapers / DIY Gardeners
Landscaping Materials Volume Calculator
Enter area and depth to get volume in m³, bulk bag count, and tonnes for gravel, topsoil, bark, sand, or hardcore.
- Wood Burners / Homesteaders
Firewood Cord & Rick Calculator
Enter your wood pile dimensions to get full cord equivalents, cubic metres, and BTU content. Verify firewood deliveries and estimate heating season needs.
- Backyard Fire Pit Owners
Fire Pit Clearance Calculator
Enter your fire pit diameter to get the required setback distance, then check nearby structures for pass/fail clearance.
- Pool Owners
Pool Chemical Dosage Calculator
Enter your current chlorine, pH, and alkalinity readings to get exact grams to add for any pool volume in litres or gallons.
Navigation & Maps
3 toolsBearings, map scales and pace counting for the trail and for orienteering.
- Hikers / Navigators / Surveyors
GPS Bearing & Distance Calculator
Enter two lat/lon coordinates to get distance in km/miles/nautical miles, true bearing, magnetic bearing, and a live map.
- Hikers / Geographers / Teachers
Map Scale Distance Converter
Enter a map scale like 1:25,000 and measure distance to get the real-world distance in km, miles, and metres. Bidirectional. Naismith walking time estimate.
- Land Navigators
Pace Count Calculator
Turn your paces per 100 m into the count for any leg, adjusted for hills, brush and darkness, with a ranger bead plan, a reverse check on paces already walked, and a printable pace card.
Boating & Knots
3 toolsAnchor scope, nautical units and rope strength.
- Sailors / Mariners
Nautical Unit Converter
Convert speed (knots, km/h, mph), distance (nm, km, miles), depth (m, ft, fathoms), pressure, and temperature. Beaufort scale lookup and passage planning.
- Sailors / Boaters
Anchor Scope Calculator
Enter water depth, tidal range, and bow height to get total rode length at your chosen scope ratio. Tidal correction, swinging circle.
- Climbing / Sailing / Rigging
Knot Strength & SWL Calculator
Select your knot and rope breaking strength to get knot efficiency, resulting strength, and safe working load at 5:1, 10:1, and 15:1 safety factors.
Pets, Poultry & Aquariums
5 toolsAges, food portions, incubation dates, stocking levels and salinity for animals in your care.
- Pet Owners
Dog Age Calculator
Free dog age to human years calculator using the accurate non-linear scale by breed size. Includes life stage and life expectancy estimate.
- Dog & Cat Owners
Pet Food Portion & Daily Calorie Calculator
Enter your dog or cat's weight, age, and activity level to get daily calorie needs and grams per day of their specific food. AAHA-based.
- Poultry Keepers / Homesteaders
Egg Incubation Calculator
Enter species and set date to get expected hatch date, candling dates, and lockdown date. Today's day counter, timeline visual, multiple clutch tracking.
- Fish Keepers
Aquarium Fish Stocking Calculator
Add species with adult size and bioload to get stocking percentage, filtration needs, and compatibility warnings. Works for freshwater and marine.
- Marine Fishkeepers / Reef Aquarists
Saltwater Aquarium Salinity Calculator
Convert between SG, PSU/ppt, and refractometer readings. Calculate exact salt grams to add or freshwater to dilute. Temperature correction included.
Shooting, Snow & Travel
3 toolsBallistic tables, ski wax choice and flight emissions.
- Hunters / Long-Range Shooters
Bullet Drop & Ballistics Calculator
Enter BC, muzzle velocity, and zero range to get drop, wind drift, and a printable range card out to 500m. MOA correction, calibre presets.
- Skiers / Snowboarders
Ski Wax Temperature Calculator
Enter the forecast snow or air temperature to find the matching wax category for skis or snowboards.
- Sustainability / Travelers
Flight Carbon Footprint Calculator
Enter departure and destination airport codes to get CO2e per passenger by seat class. Radiative forcing multiplier, round trip, offset cost.
Which tool do I need?
- Plan when to start seeds indoorsSeed Starting Date Calculator
- See sowing, transplant and harvest windows on one chartSeed to Harvest Calendar
- Fit plants into a raised bedVegetable Garden Spacing Calculator
- Fix acidic or alkaline soilSoil pH Lime & Sulfur Calculator
- Balance a compost pileCompost Carbon-to-Nitrogen Ratio Calculator
- Check that a drip system has enough pressureDrip Irrigation Zone Calculator
- Order gravel, topsoil or barkLandscaping Materials Volume Calculator
- Check that a firewood delivery is a full cordFirewood Cord & Rick Calculator
- Measure a distance on a paper mapMap Scale Distance Converter
- Work out how much anchor rode to let outAnchor Scope Calculator
- Find the expected hatch date for eggsEgg Incubation Calculator
- Decide how many fish a tank can holdAquarium Fish Stocking Calculator
Outdoors & Garden FAQ
When should I start seeds indoors?
Enter your last frost date and pick your vegetables in the seed starting calculator. It returns a calendar with the indoor start, harden-off and transplant dates for each crop.
How do I fix my soil pH?
The soil pH correction calculator estimates how much lime or sulfur to add based on your soil texture, and lays out a season-by-season application schedule.
What is a good carbon-to-nitrogen ratio for compost?
Add your browns and greens by weight to the compost ratio calculator. It shows the blended ratio with a traffic-light verdict and tells you what to add to balance the pile.
How much anchor rode should I let out?
Enter the water depth, tidal range and bow height into the anchor scope calculator. It returns the total rode length for the scope ratio you choose and includes a tidal correction.
How do I check that I bought a full cord of firewood?
Enter the dimensions of your wood pile into the firewood calculator. It converts them to full cord equivalents and cubic metres so you can compare against what was delivered.
Are the pet tools a substitute for a vet?
No. The pet feeding and probiotic tools do arithmetic on the weight and details you enter. A vet is the right source for advice about a specific animal.
Related categories
Last updated: September 30, 2026