Calculator category
Conversion Calculators
Convert common length and mass units using documented factors and visible assumptions.
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Unit Conversion CalculatorUse this unit converter to convert common length and mass units, including meters, feet, kilograms, pounds, and more.Bandwidth CalculatorCalculate transfer time from calculation mode and data amount with this bandwidth calculator; check units, factor direction, rounding, and the worked.Base64 Encode / DecodeCalculate output text from operation and text with this base64 encode / decode calculator; check units, factor direction, rounding, and the worked example.Binary CalculatorFree instant binary calculator (2026): add, subtract, multiply, divide binary numbers, convert binary ↔ decimal ↔ hex, two's complement. No sign-up.BTU CalculatorCalculate estimated cooling capacity from room area and sun/shade with this BTU calculator; check units, factor direction, rounding, and the worked.Concrete CalculatorFree instant concrete calculator (2026): get the cubic yards, meters, and 60/80 lb bags of concrete you need for a slab, footing, or column. With waste allowance.Density CalculatorFree instant density calculator (2026): solve density = mass / volume (or solve for mass or volume) in seconds. Includes density chart for water, metals, wood.Engine Horsepower CalculatorCalculate engine horsepower from measured engine torque and torque unit with this engine horsepower calculator; check units, factor direction, rounding.
All available conversion calculators
Choose the calculator by the result you need first, then check the page assumptions and sources before reusing the answer.
Unit Conversion CalculatorUse this unit converter to convert common length and mass units, including meters, feet, kilograms, pounds, and more.Converted valueBandwidth CalculatorCalculate transfer time from calculation mode and data amount with this bandwidth calculator; check units, factor direction, rounding, and the worked.Transfer timeBase64 Encode / DecodeCalculate output text from operation and text with this base64 encode / decode calculator; check units, factor direction, rounding, and the worked example.Output textBinary CalculatorFree instant binary calculator (2026): add, subtract, multiply, divide binary numbers, convert binary ↔ decimal ↔ hex, two's complement. No sign-up.DecimalBTU CalculatorCalculate estimated cooling capacity from room area and sun/shade with this BTU calculator; check units, factor direction, rounding, and the worked.Estimated cooling capacityConcrete CalculatorFree instant concrete calculator (2026): get the cubic yards, meters, and 60/80 lb bags of concrete you need for a slab, footing, or column. With waste allowance.Estimated order volumeDensity CalculatorFree instant density calculator (2026): solve density = mass / volume (or solve for mass or volume) in seconds. Includes density chart for water, metals, wood.MassEngine Horsepower CalculatorCalculate engine horsepower from measured engine torque and torque unit with this engine horsepower calculator; check units, factor direction, rounding.Engine horsepowerGas Mileage CalculatorCalculate fuel economy from distance traveled and distance unit with this gas mileage calculator; check units, factor direction, rounding, and the worked.Fuel economyGravel CalculatorCalculate estimated weight from length and width with this gravel calculator; check units, factor direction, rounding, and the worked example.Estimated weightHex CalculatorCalculate decimal from hexadecimal integer with this hex calculator; check units, factor direction, rounding, and the worked example.DecimalHorsepower CalculatorCalculate horsepower from solve for and torque with this horsepower calculator; check units, factor direction, rounding, and the worked example.HorsepowerIP Subnet CalculatorCalculate CIDR block from ipv4 address and CIDR prefix length with this IP subnet calculator; check units, factor direction, rounding, and the worked.CIDR blockMass CalculatorFree instant mass calculator (2026): find mass from density and volume, or from weight and gravity, in seconds. Clear mass vs weight explanation included.MassMolarity CalculatorCalculate molarity from solve for and molarity with this molarity calculator; check units, factor direction, rounding, and the worked example.MolarityMolecular Weight CalculatorCalculate molar mass from chemical formula with this molecular weight calculator; check units, factor direction, rounding, and the worked example.Molar massMulch CalculatorCalculate approximate bags from length and width with this mulch calculator; check units, factor direction, rounding, and the worked example.Approximate bagsOhm's Law CalculatorCalculate voltage from solve for and voltage with this ohm's law calculator; check units, factor direction, rounding, and the worked example.VoltageResistor CalculatorFree instant resistor calculator (2026): decode 4-band & 5-band color codes to ohms in seconds. Series and parallel resistance built in. Full color chart.ResistanceRoman Numeral ConverterFree instant Roman numeral converter (2026): turn any number into Roman numerals or back in seconds. Full I-V-X-L-C-D-M chart and subtraction rules.Roman numeralRoofing CalculatorCalculate area with waste from building length and building width with this roofing calculator; check units, factor direction, rounding, and the worked.Area with wasteShoe Size ConversionConvert mondopoint estimate from foot length with this shoe size conversion calculator; check units, factor direction, rounding, and the worked example.Mondopoint estimateSpeed CalculatorCalculate distance from solve for and distance with this speed calculator; check units, factor direction, rounding, and the worked example.DistanceSquare Footage CalculatorFree instant square footage calculator (2026): get the area in sq ft from length and width in seconds — perfect for flooring, paint, and tile estimates. Sq m, sq yards, acres included.Area per itemTile CalculatorCalculate estimated tiles to buy from surface length and surface width with this tile calculator; check units, factor direction, rounding, and the worked.Estimated tiles to buyTire Size CalculatorCalculate current diameter from current section width and current aspect ratio with this tire size calculator; check units, factor direction, rounding.Current diameterURL Encode / DecodeCalculate output text from operation and text with this URL encode / decode calculator; check units, factor direction, rounding, and the worked example.Output textWeight CalculatorCalculate mass from mass and mass unit with this weight calculator; check units, factor direction, rounding, and the worked example.Mass
How to choose
Use the unit conversion calculator when both units measure the same dimension, such as meters to feet or pounds to kilograms.
Conversion Calculators FAQ
Can I convert any two units?
The first version supports common length and mass units. It rejects incompatible conversions such as meters to pounds.
Where do the conversion factors come from?
The unit conversion page documents its source and review date. The implementation converts through a base unit for each dimension.