Formula categories
73 subjects across 1787 solvers, in 16 groups. A formula can sit in more than one category, so the counts add to more than the catalog. Looking for a theme rather than a subject? Formula sets group formulas by the question they answer, and the engineering hub arranges them by discipline.
Agriculture & Growing 6
Five audiences the catalog split apart on purpose; the split only works if the parent keeps them in sight of each other.
Crop Production 51 solvers
Harvest Index · Pure Live Seed · Base Saturation · Field Emergence · Dry Matter Yield · all 51 →
Farm Operations 24 solvers
Drawbar Power · Field Efficiency · Break-Even Yield · Break-Even Price · Grain Cone Volume · all 24 →
Forestry & Forest Ecology 9 solvers
Leaf Area Index (LAI) · Tree Basal Area from DBH · Stand Basal Area per Hectare · Fractional Canopy Cover from LAI · Olson's Single-Exponential Litter Decay · all 9 →
Indoor & Greenhouse 11 solvers
Yield per Watt · Leaching Fraction · Lighting Power Density · Grow Space Air Exchange · Daily Light Integral (DLI) · all 11 →
Chemistry & Process 4
The science, the unit operations, the electrochemistry and the one fermentation trade — all solution chemistry with a vessel around it.
Brewing & Fermentation 14 solvers
Malt Colour Units · Apparent Attenuation · IBU from Utilisation · Brewhouse Efficiency · Hop Utilisation (Tinseth) · all 14 →
Chemical Engineering 43 solvers
Reflux Ratio · Boilup Ratio · Space Velocity · Reaction Yield · Schmidt Number · all 43 →
Chemistry 136 solvers
Density · Boyle's Law · Raoult's Law · Charles's Law · Ideal Gas Law · all 136 →
Computing & Chips 3
Algorithms and information, and the silicon underneath them.
Computer Science 26 solvers
RSA Modulus · RSA Totient · Compression Ratio · File Transfer Time · Nyquist Sampling Rate · all 26 →
Electricity & Power 3
The field, the wiring practice and the generation: one reader follows all three.
Electrical Trade 61 solvers
Skin Depth · Conduit Fill · Voltage Divider · Current Divider · Motor Efficiency · all 61 →
Electricity & Magnetism 93 solvers
Ohm's Law · Skin Depth · Coulomb's Law · Voltage Divider · Current Divider · all 93 →
Health & the Body 3
The individual body, the population, and the everyday comfort and fitness arithmetic.
Biomedical & Clinical 21 solvers
Serum Anion Gap · Mean Arterial Pressure (MAP) · Corrected Calcium for Albumin · IV Infusion Rate (mL per Hour) · Arterial Oxygen Content (CaO₂) · all 21 →
Heat, Fluids & HVAC 4
Energy and mass moving through a fluid — and HVAC, which is that physics with a building around it.
Fluid Mechanics 129 solvers
Mach Number · Prandtl Number · Nusselt Number · Chezy Equation · Reynolds Number · all 129 →
Heat Transfer 63 solvers
Biot Number · Lewis Number · Jakob Number · Eckert Number · Graetz Number · all 63 →
HVAC & Hydronics 107 solvers
Pump System Curve · Total Dynamic Head · Stack Exit Velocity · Fan Brake Horsepower · Pipe Internal Volume · all 107 →
Thermodynamics 137 solvers
Boyle's Law · Latent Heat · Biot Number · Charles's Law · Fourier Number · all 137 →
Machines & Manufacturing 7
Size the component, cut it, then measure the plant that makes it. Also: Strength of Materials.
Additive Manufacturing 12 solvers
Hausner Ratio · Scan Time per Layer · Build Time Estimate · Powder Consumed by a Build · Carr Compressibility Index · all 12 →
Freight & Shipping 10 solvers
Pieces per Load · Shipment Density · Cube Utilisation · Chargeable Weight · Length Plus Girth · all 10 →
Industrial Engineering 20 solvers
Takt Time · Reorder Point · Machine Utilisation · Equivalent Annual Cost · Process Capability (Cp) · all 20 →
Machine Design 43 solvers
Belt Speed · Archard Wear Depth · Gear Pitch Diameter · Gear Centre Distance · Logarithmic Decrement · all 43 →
Machining & Turning 15 solvers
Bend Allowance · Bend Deduction · Limiting Drawing Ratio · Milling Table Feed Rate · Taylor Tool Life Equation · all 15 →
Materials 6
What the stuff is, and what decides how it fails: stress and stiffness, microstructure, and strength as a distribution. Also: Corrosion & Protection. Also: Welding & Joining.
Ceramics & Glass 11 solvers
Weibull Survival Probability · Weibull Strength Size Scaling · Weibull Modulus from Two Points · Median Rank Failure Probability · Vogel-Fulcher-Tammann Viscosity · all 11 →
Concrete 11 solvers
Water-Cement Ratio · Concrete Batch Yield · Gravimetric Air Content · Nurse-Saul Equivalent Age · Abrams' Water-Cement Ratio Law · all 11 →
Metallurgy & Heat Treatment 13 solvers
Lever Rule · Norton Creep Law · Vickers Hardness · Chvorinov's Rule · Hall–Petch Relation · all 13 →
Polymers & Plastics Processing 12 solvers
Deborah Number · Mould Shrinkage · Extruder Net Output · Single-Screw Drag Flow · Apparent Wall Shear Rate · all 12 →
Strength of Materials 97 solvers
Catenary Sag · Poisson's Ratio · Liquidity Index · Cable Sag Ratio · Factor of Safety · all 97 →
Mathematics 8
The tools every other group borrows, and the places they are used on their own — ratings, dice and the arithmetic of play.
Algebra 110 solvers
Midrange · Factorial · Present Value · Percent Error · Percent Change · all 110 →
Games & Ratings 16 solvers
Elo Expected Score · Pythagorean Expectation · Log5 Matchup Probability · Variance of a Sum of Dice · Glicko g Attenuation Factor · all 16 →
Geometry 111 solvers
Kite Area · Arc Length · Square Area · Cone Volume · Cube Volume · all 111 →
Probability 31 solvers
Factorial · Complement Rule · Permutations (nPr) · Combinations (nCr) · Poisson Probability · all 31 →
Statistics 74 solvers
Midrange · Percent Error · Complement Rule · Percent Difference · Elo Expected Score · all 74 →
Trigonometry 27 solvers
Arc Length · Law of Sines · Back Azimuth · Law of Cosines · Sinusoidal Model · all 27 →
Mechanics & Motion 3
Forces, energy and motion, from the first four formulas anyone meets to the full treatment.
Billiards & Cue Sports 11 solvers
Speed at Natural Roll · Cushion Rebound Angle · Cushion Rebound Speed · Tip Offset to Spin Ratio · Stun Shot — Cue Ball Speed · all 11 →
Mechanics 160 solvers
Torque · Gear Ratio · Hooke's Law · Orbital Period · Power (P = W/t) · all 160 →
Physics 255 solvers
Torque · Density · Ohm's Law · Gear Ratio · Hooke's Law · all 255 →
Money & Markets 2
Interest, loans and depreciation on one side; elasticity, surplus and what a price change actually does on the other.
Space, Flight & Modern Physics 3
Orbital mechanics is the hinge — relativity and gravitation on one side, delta-v on the other.
Aerospace & Flight 33 solvers
Drag Polar · Stall Speed · Wing Loading · Lift Equation · Rotor Solidity · all 33 →
Structures, Ground & Earth 7
Building, and the ground it stands on: the load, the soil, the survey, the shaking, and the site work.
Axle Loads & Pavement 10 solvers
Design Lane ESALs · Tyre Contact Area · Equivalent Tyre Contact Radius · Federal Bridge Gross Weight Formula · Cumulative ESALs with Traffic Growth · all 10 →
Civil & Surveying 83 solvers
Back Azimuth · Chezy Equation · Hydraulic Radius · Grade to Slope Angle · Shear Flow (q = VQ/I) · all 83 →
Rock Mechanics 37 solvers
Powder Factor · Mine Air Power · The Airway Square Law · Two Airways in Series · Pillar Factor of Safety · all 37 →
Seismology 11 solvers
Seismic Moment · Moment Magnitude (Mw) · Impedance Contrast Amplification · Fundamental Period of a Soil Site · S-Wave Velocity from Shear Modulus · all 11 →
Soil Mechanics 49 solvers
Liquidity Index · Hydraulic Gradient · Saturated Unit Weight · Water (Moisture) Content · Horton Infiltration Rate · all 49 →
Water, Air & Environment 9
What you do to a fluid before or after the public touches it. Also: Corrosion & Protection.
Air Quality & Dispersion 31 solvers
Ekman Number · Rossby Number · Holland Plume Rise · Stack Exit Velocity · Briggs Buoyancy Flux · all 31 →
Coastal & Ocean Waves 12 solvers
Wave Steepness · Wave Energy Density · Shoaling Coefficient · Deep-Water Wave Celerity · Keulegan–Carpenter Number · all 12 →
Ecology & Biodiversity 6 solvers
Pielou's Evenness (J′) · Logistic Population Growth · Shannon Diversity Index (H′) · Simpson's Index of Diversity (1 − D) · Species-Area Relationship (S = cA^z) · all 6 →
Erosion & Sediment 11 solvers
Rouse Suspension Number · API RP 14E Erosional Velocity · Finnie Erosion of a Ductile Metal · Universal Soil Loss Equation (USLE) · Bed Shear Stress in an Open Channel · all 11 →
Fire Protection & Fire Dynamics 10 solvers
t-Squared Fire Growth · Heskestad Flame Height · Thomas Flashover Correlation · MQH Hot Gas Layer Temperature · Point Source Radiant Heat Flux · all 10 →
Snow & Ice 10 solvers
Snow Gun Output Rate · R-Value of a Snow Wall · Snow Water Equivalent (SWE) · Snow Volume from Water Volume · Snow Made in a Wet-Bulb Window · all 10 →
Storm & Sky 8 solvers
Koschmieder Visual Range · Hailstone Terminal Velocity · Flat Roof Snow Load (ASCE 7) · Flash-to-Bang Distance to a Lightning Strike · Expected Annual Lightning Strikes to a Structure · all 8 →
Water & Wastewater 79 solvers
Chezy Equation · Well Efficiency · Hydraulic Radius · BOD Mass Loading · Surface Overflow Rate · all 79 →
Water Treatment 148 solvers
Density · Cylinder Volume · Glycol Dilution · Specific Gravity · Percent Blowdown · all 148 →
Waves, Light & Sound 3
One wave equation in three media: the oscillation, the ray, and the room.
Acoustics & Noise 18 solvers
Beat Frequency · Decibel Sound Level · Speed of Sound in Air · Combining Sound Levels · Sound Transmission Loss · all 18 →
Optics 27 solvers
Malus's Law · Apparent Depth · Brewster's Angle · Thin Lens Equation · Lens Power in Diopters · all 27 →