🛠️ 17 Hobby Calculators
Real numbers for your hobby — what a 3D print actually costs, how many gallons your tank really holds, how much substrate to buy, and how long to cut a dipole.
3D Printing, Aquarium & Radio Calculators
Each tool is interactive: price a print with material, electricity, depreciation and failure overhead; convert any tank shape to gallons and liters; plan gravel, sand or aqua soil by the bag; and get dipole cut lengths for any frequency.
3D Printing Cost Calculator
Free 3D printing cost calculator: filament, electricity (18.83¢/kWh US avg), depreciation and failure rate. A 150 g PLA ...
Fish Tank Volume Calculator
Free fish tank volume calculator for 6 shapes. US gallons (231 cu in each), liters, UK gallons, water weight at 8.34 lb/...
Aquarium Substrate Calculator
Free aquarium substrate calculator: pounds, kg, liters, and bag counts from tank footprint and depth. A 20-long needs ~2...
Dipole Antenna Calculator
Free dipole antenna calculator: 468 ÷ f MHz gives half-wave length — a 40 m dipole cuts to 65 ft 5 in. Presets for 160 m...
ABV Calculator (Alcohol by Volume)
Free ABV calculator: enter OG and FG for alcohol by volume via (OG − FG) × 131.25 plus a high-gravity formula, ABW, calo...
Priming Sugar Calculator for Bottling Beer
Free priming sugar calculator for bottling beer: batch size, temp, and CO2 target in, grams out. A 5-gallon ale at 2.5 v...
Hydrometer Temperature Correction Calculator
Hydrometer temperature correction calculator: a 1.050 wort reads just 1.044 at 100°F. Fix readings for 60°F and 68°F cal...
IBU Calculator
Free IBU calculator using the Tinseth formula. Add up to 3 hop additions for total and per-addition IBUs. American IPAs ...
Brix Calculator: Convert Brix to Specific Gravity and Back
Free Brix calculator converts Brix to specific gravity and back — 12 Brix ≈ SG 1.048 — with a wort correction factor for...
Epoxy Resin Calculator: How Much Epoxy Do I Need?
Epoxy resin calculator for tabletops, river tables, and molds. Converts inches to ounces (divide by 1.805), splits resin...
Candle Wax Calculator
Free candle wax calculator: water weight × 0.86 gives wax per container, fragrance oil at 6–10% load, and cost per candl...
Board Foot Calculator
Free board foot calculator: thickness × width × length ÷ 12. Board feet per piece, totals, and cost with 2026 hardwood p...
Firewood Cord Calculator
Free firewood cord calculator — convert stack length, height & depth to full cords (128 cu ft), face cords & dollar valu...
Yarn Yardage Calculator: How Much Yarn Do I Need?
Free yarn yardage calculator: how much yarn you need by project and weight — 1,125–1,625 yds for a worsted sweater — plu...
Keg Carbonation Calculator (Set-and-Forget PSI + Line Length)
Free keg carbonation calculator: enter beer temp and CO2 volumes to get regulator PSI — 2.5 vols at 38°F = 11.2 psi — pl...
Aquarium CO2 Calculator: CO2 ppm from KH & pH
Free aquarium CO2 calculator: enter KH and pH to get dissolved CO2 in ppm via 3 × KH × 10^(7−pH). Target 20-30 ppm for p...
Voltage Drop Calculator
Free voltage drop calculator for 12V–240V circuits. Uses NEC Table 8 resistance (12 AWG = 1.93 Ω/1,000 ft) to check any ...
Why Run the Numbers First
Hobby math has real stakes: a mispriced print eats your margin, an overstocked tank stresses fish, too much gravel is money in a bucket, and a dipole cut short means starting over with new wire. These calculators use the exact constants that matter — 231 cubic inches per US gallon, 8.34 pounds per gallon of water, 468 ÷ MHz for a half-wave dipole — so you buy and cut right the first time.