Field-ready calculators for engineers: HVAC loads, flows, pressures, materials and more—reliable results, instant outputs.
Audio Tools 1
Measure integrated, short-term and momentary LUFS plus true-peak and LRA per EBU R128 / ITU-R BS.1770. Free in-browser loudness meter for podcasts and music.
Calculators 55
Engineering Calculators 39Decode 4, 5, 6 band resistor colors to ohm value and tolerance, reverse-lookup E12/E24/E48/E96 parts, and check power rating, max current and voltage.
Wheelchair ramp calculator for 2010 ADA Standards & IBC/A117.1: slope percent, length, landings, handrail length, and 1:8/1:10 alteration compliance.
Area & square footage calculator for rectangle, circle, triangle and more. Add a waste factor and unit price to estimate material quantity and total cost.
Asphalt calculator for driveways, roads and parking lots: estimate hot mix tonnage, cubic yards, metric tonnes, aggregate base and total cost by area and thickness.
Free air conditioner size calculator: find how many BTU you need by room size, then convert BTU to tons & kW with cooling/heating modes.
Compute maximum deflection, bending moment and shear force for simply supported and cantilever beams under point or distributed loads. Free for engineers.
Blueprint measurement tool — upload architectural drawings, calibrate with a known dimension, then measure any distance on floor plans and elevations.
Free brick calculator: bricks per m2, mortar bags and waste for any wall. Deducts door and window openings for an accurate brickwork estimate.
ASHRAE 62.1 CFM calculator for HVAC fan & duct sizing. Compute air flow from room size, air changes, or BTU load with altitude density correction & L/s output.
Concrete calculator for slabs, columns, footings, curb and stairs. Get cubic yards, m3, 60/80 lb bag counts and the M20 mix ratio take-off.
Drywall calculator: estimate 4x8/4x10/4x12 sheets, sheet weight, screws, tape and compound for walls and ceilings, with 5/8" Type X fire-rated guidance.
ASHRAE Darcy-Weisbach pressure drop calculator for HVAC ducts and water pipes. Friction and fitting K-factor losses, equivalent diameter, velocity check.
Duct size calculator for HVAC: get round or rectangular dimensions, equivalent round diameter, friction loss per 100 ft, and an ASHRAE velocity check.
Calculate Floor Area Ratio (FAR/FSI/FSR), chargeable buildable area, lot coverage and minimum open space for zoning compliance. For architects and planners.
Flow rate and pipe sizing calculator for volumetric flow, velocity and pipe area. Convert m³/h, L/min, GPM, CFM and check velocity against code limits.
Free gear ratio calculator: output RPM, torque multiplication, compound trains, plus AGMA service factor and gearbox sizing for motor reduction drives.
Grade calculator with slope ratio (V:H) and code-compliance pass/fail. Compute grade percent, angle and ratio against ADA, AASHTO and drainage limits.
Free gravel calculator: find how much gravel you need for a driveway or path in cubic yards, tons and bags, plus the total cost with a waste/compaction margin.
Estimate insulation needed for walls, attics and ceilings. Calculate area, R-value, thickness and ballpark material cost for fiberglass, foam or cellulose.
Material weight calculator for steel, aluminum, copper and metal. Get total weight plus weight per meter and per foot for plates, bars, tubes and pipe.
Mulch calculator for landscaping: volume for rectangular, circular and triangular beds in yd³, ft³, m³, plus bags-vs-bulk cost and waste overage.
Calculate occupant load and IBC 2021 egress: occupancy load factor, exits, stairway width, travel distance. Verify your design and Certificate of Occupancy.
Paint calculator with spread rate, two coats and textured-surface presets. Estimate liters & gallons and the real quantity to order, not just sq ft per gallon.
Parking ratio calculator: required spaces by building type, editable ITE/zoning ratio, ADA & van accessible spaces, and parking lot area estimator.
Pipe volume calculator: internal volume from inner diameter and length in liters/gallons, plus pipe weight per meter (empty + water-filled) for steel, PVC, copper.
Pressure drop calculator for pipes and ducts. Compute pressure loss for water, air and gas with Darcy-Weisbach — for HVAC, plumbing and fluid mechanics.
Compute dew point, wet bulb, humidity ratio, enthalpy and specific volume of moist air with altitude correction, plus an ASHRAE 55 comfort check.
Calculate pulley speed ratio, output RPM, belt length, wrap angle and belt speed for V-belt and flat-belt drives, with a 120-degree wrap check.
Calculate rebar quantity, length and weight for concrete slabs, then verify the steel-to-concrete ratio (kg/m³) against ACI/EC2 benchmark ranges. Free.
Estimate HVAC/AC refrigerant charge by capacity, line set length and pipe diameter, with A2L charge-limit check. R-410A, R-32, R-454B, R-22, R-134a, R-404A.
Size walk-in cold rooms and freezers fast: get the heat load in BTU/hr, tons and kW with full transmission, product, latent and infiltration breakdown.
Roofing calculator: estimate roof area by pitch or angle, shingle bundles, metal panels, underlayment, ridge cap and drip edge for a pro takeoff.
Free scale converter for drawings, models and maps. Convert metric, imperial (1:48) and ISO 5455 engineering scales, plus check A1/A3 paper fit.
Slope calculator for rise over run: percent grade, angle in degrees, ratio and length. Checks ADA ramp, roof pitch X:12, driveway and pipe-fall code limits.
Square footage calculator for flooring, tile, paint and drywall. Get area in m², ft², yd², in², cm², plus waste factor, units needed and total cost.
Stair calculator with IRC/IBC code pass-fail checks. Get riser count, rise, run, stringer length, pitch angle and headroom compliance for safe stair design.
Tile calculator for floors and walls: estimate tiles, full boxes, thinset adhesive bags, grout bags and cost by square footage or room size, with waste.
Torque calculator with bolt torque mode: reverse-solve force or lever arm, and get bolt clamp load (preload) from T = K × D × F. N·m, lb·ft, kN.
Volume calculator for sphere, cone, cube, cylinder, tank, capsule, pyramid and ellipsoid. Converts m³/L/gal/ft³ and shows fill weight by density.
Health & Fitness 1Calculate feels-like temperature with wind chill, heat index, dew point, WBGT wet bulb globe temperature and OSHA/ACGIH heat-stress work-rest guidance.
HVAC Calculators 6HDD & CDD calculator with base 65F/18C, 1991-2020 climate normals, IECC zone, plus building energy & fuel-cost estimate for ASHRAE 90.1 work.
Convert U-value (thermal transmittance) and R-value, build multi-layer wall assemblies, add air films, and check IECC climate-zone code compliance.
Calculate ASHRAE 62.1 outdoor air from Rp and Ra in CFM and L/s, then run a pass/fail check on your design or measured airflow versus the minimum OA.
ACH calculator with ASHRAE 62.2 minimum, CFM to ACH conversion, clearance time and annual energy cost for HVAC, cleanroom and isolation design.
Convert temperature, RH & dew point via Magnus-Tetens. Get wet bulb, humidity ratio, absolute humidity & vapor pressure for HVAC condensation, ASHRAE comfort.
Free HVAC load & BTU calculator: size AC tonnage with Manual J sensible/latent split, solar gain and an ACCA Manual S oversizing compliance check.
Math Calculators 2Add, multiply, divide complex numbers and combine parallel impedances. Rectangular to polar conversion, phasors, De Moivre powers and roots with R + jX steps.
Differentiate or integrate a function symbolically, then evaluate the result at a point or compute a definite integral over [a, b]. Free, instant, no sign-up.
Wire Calculators 7Convert AWG wire gauge to mm and mm2 cross-section, with kcmil, nearest IEC 60228 size, NEC ampacity and copper resistance for wire sizing.
Convert SWG (Standard Wire Gauge) to millimeters instantly. Calculate diameter and cross-sectional area with the British wire gauge converter.
Three-phase voltage drop calculator with operating-temperature correction and a NEC 3%/5% or IEC pass/fail check for Delta and Wye feeders, copper or aluminum.
Voltage drop calculator with NEC 3%/5% and IEC pass/fail check. Get the minimum compliant AWG for DC, single- and three-phase runs in copper or aluminum.
Estimate wire ampacity with derating factors for temperature and conduit fill. Reference tool based on NEC guidelines. Always consult local electrical codes.
Free AWG wire gauge calculator: diameter, cross-section area, resistance, plus built-in NEC ampacity and 3% voltage-drop check for copper and aluminum.
Wire resistance & voltage drop calculator with NEC 3%/5% check. AWG/mm/inch, °C/°F, 6 metals, temperature compensation and I²R power loss.
Conversion 37
Area Conversion 4Convert acres to ping (坪) instantly. 1 acre = 1224.17 ping using the Taiwan/Japan land unit (1 ping ≈ 3.306 m²). Free acre→ping calculator for real-estate use.
Convert hectares to ping (坪) instantly. 1 ha = 3024.99 ping using the Taiwan/Japan unit. Free ha→坪 calculator for metric-to-East-Asia land area conversion.
Convert ping (坪) to acres instantly. 1 ping = 0.000817 acre (1224.17 ping = 1 acre). Free 坪→acre calculator for Taiwan/Japan land deals in US/UK measure.
Convert ping (坪) to hectares instantly. 1 ping = 0.0003306 ha (3025 ping = 1 ha). Free 坪→ha calculator for converting East Asian land units to metric hectares.
Electric Charge Conversion 1Convert electric charge units instantly. Coulombs, milliCoulombs, microCoulombs, nanoCoulombs, picoCoulombs, Amp-hours, milliamp-hours.
Energy Conversion 6Convert BTU to Joules (BTU to J) instantly with our free online converter. Accurate 1 BTU = 1055.06 J formula, examples, conversion table and step-by-step...
Convert BTU to Kilojoules (BTU to kJ) instantly with our free online converter. Accurate 1 BTU = 1.05506 kJ formula, examples, conversion table and...
Convert Joules to BTU (J to BTU) instantly with our free online converter. Accurate 1 J = 0.000947817 BTU formula, examples, conversion table and...
Convert Joules to Calories (J to cal) instantly with our free online converter. Accurate 1 J = 0.239006 cal formula, examples, conversion table and...
Convert Calories to Joules (cal to J) instantly with our free online converter. Accurate 1 cal = 4.184 J formula, examples, conversion table and...
Convert Kilojoules to BTU (kJ to BTU) instantly with our free online converter. Accurate 1 kJ = 0.947817 BTU formula, examples, conversion table and...
Flow Rate Conversion 1Convert all flow rate units instantly. Liters per second, minute, hour, cubic meters, gallons per minute, cubic feet in one tool.
Frequency Conversion 3Convert hertz to megahertz (Hz to MHz) with SI-exact 10^-6 factor. Free converter for RF, broadcasting, and CPU clocks with BIPM-precision arithmetic.
Convert megahertz to hertz (MHz to Hz) using exact SI factor 10^6. RF, SDR and DSP-grade converter with formulas, tips and atomic-clock-traceable precision.
Convert kilohertz to hertz (kHz to Hz) with SI-exact 10^3 factor. Free audio, radio and RF converter with BIPM-compliant precision and edge-case handling.
Fuel Consumption Conversion 4Convert litres per 100 km to litres per 100 miles instantly. 1 L/100km = 1.609344 L/100mi because 100 miles is 160.9344 km — the linear km-to-mile ratio.
Convert litres per 100 km to US miles per gallon instantly. MPG = 235.215 / L100km — the inverse relationship between metric and US fuel-economy units.
Convert miles per gallon UK to miles per gallon US instantly. 1 MPG UK = 0.83267 MPG US because the imperial gallon is larger than the US gallon (4.546 vs 3.785 L).
Convert miles per gallon US to miles per gallon UK instantly. 1 MPG US = 1.20095 MPG UK because the imperial gallon is 20% larger than the US gallon (4.546 vs 3.785 L).
Power Conversion 6Convert all power units instantly. Watts, kilowatts, megawatts, horsepower, BTU per hour, foot-pounds per second in one tool.
Convert BTU per hour to watts instantly: 1 BTU/hr = 0.29307107 W. Free BTU/hr to W calculator for HVAC sizing, AC capacity and heating load specs.
Convert dBm to watts using the logarithmic formula P(W) = 10^((dBm-30)/10). RF / microwave converter with link-budget tips, ITU-R and IEEE references.
Convert horsepower to kilowatts using mechanical hp (745.6999 W). Auto, marine and industrial converter with PS / SAE / DIN definitions and worked examples.
Convert Kilowatts to Megawatts (kW to MW) instantly with our free online converter. Accurate 1 MW = 1000 kW formula, examples, conversion table and...
Convert watts to BTU per hour instantly: 1 W = 3.41214 BTU/hr. Free W to BTU/hr calculator for HVAC sizing, heat-pump rating and US-spec equipment matching.
Pressure Conversion 1Convert millimetres of mercury to torr. 1 mmHg = 1 Torr by historical definition (both ≈ 133.322 Pa). Free mmHg→Torr calculator for vacuum, medical and meteorology use.
Temperature Conversion 10Convert Celsius to Kelvin (°C to K) instantly with our free online converter. Accurate K = °C + 273.15 formula, examples, conversion table and step-by-step...
Convert Celsius to Rankine (°C to °R) instantly with our free online converter. Accurate °R = (°C + 273.15) × 9/5 formula, examples, conversion table and...
Convert Fahrenheit to Kelvin instantly: K = (°F − 32) × 5/9 + 273.15. Free °F to K calculator with absolute-zero awareness and decimal precision.
Convert Fahrenheit to Rankine instantly: °R = °F + 459.67. Free °F to °R calculator using the Rankine absolute scale common in US engineering thermodynamics.
Convert Kelvin to Celsius (K to °C) instantly with our free online converter. Accurate °C = K − 273.15 formula, examples, conversion table and step-by-step...
Convert Kelvin to Fahrenheit instantly: °F = (K − 273.15) × 9/5 + 32. Free K to °F calculator with absolute-zero awareness, decimal precision, no signup.
Convert Kelvin to Rankine (K to °R) instantly with our free online converter. Accurate °R = K × 9/5 formula, examples, conversion table and step-by-step...
Convert Rankine to Celsius (°R to °C) instantly with our free online converter. Accurate °C = (°R − 491.67) × 5/9 formula, examples, conversion table and...
Convert Rankine to Fahrenheit instantly: °F = °R − 459.67. Free °R to °F calculator for US engineering thermodynamics and HVAC computations.
Convert Rankine to Kelvin (°R to K) instantly with our free online converter. Accurate K = °R × 5/9 formula, examples, conversion table and step-by-step...
Voltage Conversion 1Convert all voltage units instantly. Volts, millivolts, microvolts, kilovolts, megavolts in one tool. Free online converter with formulas and conversion table.
Developer Tools 1
Utilities 1Free IPv4 subnet calculator with CIDR to subnet mask, Cisco wildcard mask, VLSM splitting, binary view, and reverse host sizing (pick the prefix for N hosts).
Geography & Mapping Tools 1Free carbon footprint calculator for your household. Track CO2 emissions per year from transport, flights, home energy, diet & shopping, plus offset cost.
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