Gem & Jewelry Laboratory
Standardized carat measurements, karat alloy gold purity calculations, Troy ounce precious metal valuations, and historic UK assay hallmark decoding.
1. Gemstone Shape & Specific Gravity
2. Physical Dimensions (mm)
3. Estimated Carat Weight & Aspect Ratio
Explore Additional Utilities
Blanket size — horse length ↔ rug size in inches/cm
Calculate horse blanket (rug) sizing from point of shoulder to center of tail measurements in inches, centimeters, and UK/EU sizes.
Length Converter
Convert between meter, kilometer, centimeter, mile, yard, foot, inch, and more.
Telescope Magnification Calculator
Calculate telescope magnification, exit pupil, and resolving limit from focal lengths and aperture.
Blood Glucose Converter
Convert blood glucose levels between mmol/L and mg/dL, with diabetic range assessments and HbA1c approximations.
Cycling FTP & Power Zone Calculator
Calculate personalized cycling power training zones (Coggan 7-zone model) based on your Functional Threshold Power (FTP) in watts.
NPK Fertilizer Blend Designer
Calculate exact commercial fertilizer weights (Nitrogen, Phosphate, Potash) required to hit crop nutrient targets.
Drug Concentration Converter
Convert pharmaceutical concentrations between % w/v, mg/mL, and mol/L using substance molecular weight presets.
Dog Age ↔ Human Age Equivalent
Calculate the human age equivalent of a dog based on their age and breed size category (small, medium, large, or giant), using modern veterinary curves.
Body Surface Area (BSA) Calculator
Calculate body surface area (BSA) for clinical dosing using Mosteller, DuBois, Haycock, and Gehan-George formulas.
Exposure Triangle & F-Stop
Calculate absolute stop adjustments, exposure reciprocal tradeoffs, f-stop quotients, and ISO noise tradeoffs.
Hot water demand — occupants ↔ liters per hour needed
Estimate peak hot water demand in liters per hour and size standard water heater tanks or tankless flow rates.
Egg Size Converter
Convert egg counts and liquid weights across standard small, medium, large, and extra-large eggs.
DPI / PPI Converter
Convert image pixel dimensions into physical print sizes (inches/cm) at any target resolution.
Visible light transmittance ↔ tint level
Calculate Visible Light Transmittance (VLT) performance ratios and visual interior glare profiles.
Sugar Syrup Ratio Calculator
Calculate water and sugar ratios for simple, rich, and Demerara syrups by volume and weight.
Elastic Stretch Ratio Calculator
Calculate the stretch percentage and relaxed vs. stretched lengths of elastics or stretch fabrics.
Specific heat capacity — J/kg·K ↔ BTU/lb·°F
Convert between specific heat capacity units including J/kg·K, kJ/kg·°C, BTU/lb·°F, and cal/g·°C.
Zipper Length & Size Converter
Convert zipper lengths between centimeters and inches, and explore standard zipper gauge size applications.
Notarial Fee & Page Tier Calculator
Calculate official notary fees based on document page counts, copy requirements, travel, and custom tier structures.
Pipe Flow Rate Calculator
Calculate water flow rate, velocity, and capacity under gravity or pressurized nozzle flow.