Conversion & engineering tools
Unit converters, electronics helpers and mechanical engineering calculators — with the formulas spelled out.
Most popular
3D Model Viewer (STL/OBJ)
Preview STL and OBJ files in 3D — orbit, measure and inspect before printing.
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Aspect Ratio Calculator
Simplify W:H, match common ratios, scale sizes.
popular
Cooking Measurement Converter
Cups ↔ grams with per-ingredient densities.
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DPI & Pixel Size Calculator
Screen PPI, and pixels ↔ physical print size.
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Fuel Economy Converter
MPG (US/UK) ↔ L/100 km ↔ km/L in one step.
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Ohm's Law Calculator
Any two of V, I, R, P — get all four.
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Resistor Color Code Calculator
4- and 5-band colors → value, or value → colors.
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Universal Unit Converter
Length, mass, temperature, pressure, energy and more.
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Wind Chill, Heat Index & Dew Point
What the temperature actually feels like.
Unit & Everyday Converters
Cooking Measurement Converter
Cups ↔ grams with per-ingredient densities.
popular
Fuel Economy Converter
MPG (US/UK) ↔ L/100 km ↔ km/L in one step.
popular
Universal Unit Converter
Length, mass, temperature, pressure, energy and more.
Decibel (dB) Converter
Ratios ↔ dB for power and amplitude, plus dBm ↔ watts.
Electronics
Ohm's Law Calculator
Any two of V, I, R, P — get all four.
popular
Resistor Color Code Calculator
4- and 5-band colors → value, or value → colors.
Active Filter Designer (Sallen-Key)
Butterworth, Chebyshev or Bessel — component values and Bode plot.
Antenna Radiation Pattern Explorer
Polar plots of dipoles, Yagis and phased pairs — see why more elements mean a narrower beam.
Capacitor Charge Calculator
RC time constant, charge curve and stored energy.
E-Series Resistor Solver
Best E12–E96 resistor or pair for any value or ratio.
LED Series Resistor Calculator
The right resistor for any LED and supply voltage.
Room Modes & Speaker Placement
Find your room’s problem bass frequencies and where to put the speakers.
Voltage Divider Calculator
Vout from R1/R2, or the R2 needed for a target voltage.
Wi-Fi Coverage Planner
Draw your floor plan, place the router and see the signal heatmap.
Screens, Print & Ratios
Mechanics & Structures
Construction & Workshop
3D Model Viewer (STL/OBJ)
Preview STL and OBJ files in 3D — orbit, measure and inspect before printing.
3D Print Cost & Time Calculator
Material, time, energy and failure-adjusted print cost.
CNC Feeds & Speeds Calculator
RPM and feed rate for router and mill cutters.
Cut List Optimizer
Fit your parts onto the fewest boards or bars (1D).
Roof Pitch & Rafter Calculator
Rafter lengths, cut angles and pitch conversions.
Sheet Goods Cut Optimizer
Nest rectangular parts on plywood or MDF sheets (2D).
Stair Calculator
Riser and tread sizes that are safe and comfortable.
Home & Energy
Kitchen & Food
Baker's Percentage & Dough Calculator
Turn baker’s percentages into a gram-by-gram recipe.
Brewing ABV & Recipe Calculator
ABV, attenuation, calories, priming sugar and Tinseth IBU.
Coffee Brew Ratio & Extraction Calculator
Dose, water and extraction yield on the SCA control chart.
Sous Vide Time & Safety Calculator
Come-up time and pasteurization hold for safe sous vide.
About these tools
Conversion and engineering utilities for daily technical work: unit conversion across length, mass, pressure, energy and data, plus electronics helpers like Ohm’s law, resistor codes and voltage dividers, and mechanics calculators for gears, beams and torque. Values update instantly and the underlying relations are always spelled out.