Calculators index.
All 23 engineering and trade calculators. Each calculator shows the formula, a worked example and a PDF of your result.
All calculators
Beam Span Calculator
Simply-supported beam analysis — bending stress, deflection, pass/fail check. Wood (Douglas Fir, SPF, SYP) and steel W-shapes. Includes the formula, a worked
Board Foot Calculator
Calculate board feet for lumber with nominal vs actual dimensions, waste factor, and price total. Handles dimensional lumber and hardwood S4S.
Boiling Point of Water Calculator
Boiling point of water at any altitude or pressure, in °C and °F. Uses the IAPWS-IF97 standard and the standard atmosphere. Includes altitude and pressure tables.
Bolt Torque Calculator
Compute the recommended tightening torque for any bolt given grade, diameter, and lubrication state. Uses the K-factor formula T = K × D × P.
Concrete Volume Calculator
Calculate concrete volume for slabs, footings, and post holes in cubic yards, cubic meters, and number of 60/80 lb bags. With waste factor. Includes the
Drill Bit for Screw Size Calculator
Find the right pilot, tap, or clearance drill for any screw size given the material. Wood, metal, plastic — each handled correctly. Includes the formula, a
Duct Size Calculator
Calculate round duct diameter and rectangular equivalent for a given CFM at standard friction class (0.08 in. w.c. per 100 ft). Includes the formula, a worked
Feet and Inches Converter
Convert feet and inches to cm, meters and decimal feet, or cm to feet and inches to the nearest 1/16 in. Accepts fractions like 5 3/8. Height table.
Gas Pipe Sizing Calculator & Chart
Size Schedule 40 gas pipe for natural gas or propane with IFGC Equation 4-1. Enter load in BTU/h or CFH, run length and pressure drop. Includes a capacity chart.
Heat Index Calculator & Chart
Calculate the heat index from temperature and humidity with the NWS formula. See the NWS danger level in °F or °C, with the full heat index chart included.
Heat Loss Calculator
Calculate heat loss through walls, windows, and roofs from R-value (or U-value), area, and temperature difference. Imperial (BTU/h) and SI (watts) units.
Ideal Gas Law Calculator
Ideal gas law calculator: enter three of pressure, volume, moles and temperature to find the fourth. PV = nRT with the exact gas constant and unit options.
LED Resistor Calculator
Calculate the current-limiting resistor for an LED given supply voltage, LED forward voltage, and desired current. Includes the formula, a worked example,
Log Board Foot Calculator
Log board foot calculator: board feet in a log by the Doyle, Scribner Decimal C and International 1/4-inch log rules, with formulas and a log scale table.
RPM Calculator
Convert between RPM and surface feet per minute (SFM) or m/min for machining. Includes material preset SFM ranges for aluminum, steel, stainless, brass...
Ohm's Law Calculator
Ohm's law calculator: enter any two of voltage, current, resistance or power to get the other two. V = I × R and P = V × I, with examples and a resistor wattage check.
Pipe Pressure Drop Calculator
Calculate friction pressure loss in a pipe given flow rate, fluid, pipe size, and length. Uses the Darcy-Weisbach equation with the Swamee-Jain explicit...
Slope Calculator
Slope calculator: convert rise and run to percent grade, angle in degrees, 1:X ratio and roof pitch. Includes ADA ramp limits and conversion tables.
Solar Panel Angle Calculator
Optimal fixed and seasonal tilt angle for a solar panel given latitude. Year-round, summer, winter, and per-month optimal angles. Includes the formula, a
Voltage Divider Calculator
Calculate the output voltage of a resistor voltage divider given Vin, R1, and R2. Plus current draw, power dissipation, and standard E12/E24 resistor pair...
Water Weight Calculator
How much does water weigh? A US gallon of water is 8.33 lb at 68 °F. Enter any volume and temperature to get the weight in lb and kg. Density table included.
Wind Chill Calculator & Chart
Calculate wind chill from air temperature and wind speed with the NWS formula. Works in °F or °C and mph, km/h, m/s or knots. Full wind chill charts included.
Wire Size Calculator
Find the correct AWG wire gauge given amperage, run length, voltage, and allowable voltage drop. Includes NEC ampacity check. Includes the formula, a worked