Unitly Blog
Practical explanations, worked examples and honest trade-offs for everyday measurements, digital systems and science.
Concentration, density and molarity: read the quantity first
Similar-looking compound units can describe different measurements. Here is what a fixed-factor converter can and cannot connect.
GB and GiB: why the same drive shows a different number
A drive advertises 500 GB and an application displays a number closer to 465.66. That difference can be a naming convention rather than lost data.
Celsius and Fahrenheit: a reading is different from a temperature change
Celsius, Fahrenheit and Kelvin use both scale factors and offsets. Knowing what your value means prevents a common mistake.
Will it fit? Convert furniture dimensions before measuring the doorway
A desk can fit the room and still fail to pass through the doorway. Product listings often give one set of dimensions in inches, while a room plan uses centimetres.
Net, gross and tare: make a package mass comparison useful
A parcel label and a supplier specification may both mention weight while referring to different amounts. One can include the box and packing; another can describe only the contents.
Oven settings in Celsius and Fahrenheit: convert the reading, keep the cooking context
A recipe specifies 180 °C and the oven dial uses Fahrenheit. That is an absolute-temperature conversion, not a temperature-difference problem.
Square metres, square feet and flooring: separate area from the order allowance
A room plan gives 42 m² and flooring is sold by the square foot. Converting the measured area is straightforward; turning it into an order requires more decisions.
Which cup? Read a recipe volume before changing the measuring jug
A recipe says one cup, the measuring jug shows millilitres, and a conversion chart seems to disagree with both. The word cup does not guarantee a universal volume.
From km/h to mph: a road-speed conversion is only the start of a trip estimate
A route estimate uses 90 km/h while a vehicle display or planning document uses mph. Translating that speed helps readers compare like units.
Decimal hours are not clock minutes: read a timesheet without losing time
A timesheet records one hour thirty minutes, while a spreadsheet expects decimal hours. Entering 1.30 is a tempting mistake: the decimal fraction means thirty hundredths of an hour, not thirty minutes.
Degrees to radians: make an arc-length calculation agree with its angle
A drawing labels an angle in degrees, but an arc-length formula expects radians. The number 45 is not ready for that equation until its unit is converted.
Density and a liquid volume: build a mass estimate with compatible units
A supplier gives a liquid density in g/cm³ and a container volume in litres. The mass estimate needs those values to speak the same dimensional language.
Bar and psi are units; gauge and absolute are pressure references
An instrument reads 2.2 bar and a specification uses psi. Before converting, check the pressure reference.
Kilowatt-hours on a meter: convert energy without assuming an electricity price
An electricity meter records an energy quantity, often in kilowatt-hours. A device label records a power rate in watts.
Horsepower needs a definition: compare hp, PS and kilowatts carefully
Two equipment listings both say horsepower but use different definitions. Mechanical horsepower and metric horsepower are close enough to invite casual comparison, yet they are not the same unit.
Combining mpg records: total distance and fuel beat an unweighted average
Two trips can return different economy figures even when their combined fuel use is easy to measure. Averaging the two mpg numbers without weighting can give the wrong overall result.
Hertz, period and a clock rating: understand what a frequency actually counts
A signal specification gives 2.4 MHz, while a timing calculation expects cycles per second. Converting the frequency is the first step; identifying the cycle being counted is just as important.
Kilograms do not become newtons by relabelling: keep mass and force separate
A loading document gives a force in newtons while a scale or catalogue describes a mass in kilograms. Those quantities are connected by a physical model, not merely by changing the unit label.
An accelerometer reading in g: separate the reference unit from the sensor context
An accelerometer reports a value in g, but a calculation expects m/s². The unit g₀ is a standard-gravity reference, not a claim that the device measured local gravity exactly.
Torque-wrench units: avoid the twelve-fold mistake between pound-feet and pound-inches
A torque specification is useful only when its unit survives the handoff to the tool. Pound-force feet and pound-force inches look similar on a quick note, but differ by a factor of twelve.
Litres per minute and tank filling: distinguish the rate from the volume
A pump listing gives litres per minute and a tank volume is described in gallons. A unit translation can align the figures, but estimating fill time needs the volume actually to be added and a representative.
RPM to radians per second: prepare a rotational-power calculation
A shaft speed is listed as 1,500 rpm and a rotational equation uses angular velocity in radians per second. The conversion must account for both the angle in a revolution and the seconds in a minute.
Bits, bytes and download estimates: translate a rate before estimating the wait
A connection is advertised at 100 Mbit/s and a download display reports MB/s. The byte-versus-bit distinction explains a factor of eight before overhead enters the discussion.
mAh and coulombs: a battery capacity label measures charge, not energy
A battery label gives 2,400 mAh. That is a charge-capacity figure, not a complete energy specification.
Volts to millivolts: preserve the RMS, peak or DC label
A sensor specification describes a 3.3 V signal and a test report uses millivolts. The prefix conversion is simple, but the reading’s reference and convention must travel with it.
Microamps and milliamps: compare device current in the same operating mode
A device data sheet reports sleep current in microamps and operating current in milliamps. Translating both into one unit helps, but combining the operating modes without their durations can obscure the actual demand.
4.7 kΩ is not the complete resistor specification: keep tolerance and conditions
A parts list says 4.7 kΩ and a meter shows ohms. Converting the nominal value is only part of a useful comparison.
0.1 µF, 100 nF and the capacitor details a prefix cannot tell you
A schematic asks for 0.1 µF and a supplier lists 100 nF. Those capacitance values are equivalent, but the equivalence does not make every component suitable.
Millihenries to microhenries: compare an inductor beyond its nominal value
Two inductors share a nominal value but their data sheets use different prefixes. Converting 2.2 mH to microhenries removes that naming difference.
Tesla and gauss: keep a magnetic reading’s component and location
A magnetic sensor reports millitesla while another document uses gauss. The values can be translated, but a field reading still needs its location, orientation and quantity type.
Webers and maxwells: distinguish magnetic flux from coil linkage
A coil calculation may mention flux in webers or flux linkage across several turns. The unit label alone does not settle which quantity was supplied.
Lux to foot-candles: make a lighting survey’s measurement plane clear
A lighting survey records 500 lux at a desk and a comparison document uses foot-candles. Converting the number aligns the illuminance unit.
Nits and foot-lamberts: compare display measurements under matching conditions
A display listing gives nits, while a projection document uses foot-lamberts. Both describe luminance, but the unit conversion is not the whole comparison.
Moles and millimoles: name the chemical entity before counting it
A preparation note gives 0.25 mol and a worksheet asks for millimoles. Prefix conversion does not change the entity being counted, but that entity must be named.
Why g/mol and kg/kmol have the same number
A chemistry source reports molar mass in g/mol and an engineering worksheet uses kg/kmol. The two numerical values can match because both sides of the ratio change together.
mg/L and g/L: keep a dilution factor separate from the unit conversion
A laboratory result is expressed in mg/L and a preparation worksheet expects g/L. Translating 250 mg/L does not account for dilution, sample recovery or a change in the volume basis.
Wh/kg at cell and pack level: compare the mass boundary before the number
A battery comparison quotes specific energy in Wh/kg. One figure can describe a cell, another a complete pack with housing and electronics.
Specific heat and heating energy: the temperature change needs an interval
A heating estimate combines mass, specific heat capacity and temperature change. The units can look complicated because energy, mass and a temperature interval all appear in one ratio.
A heat-transfer coefficient is not a heat rate: keep area and temperature difference
A coefficient is listed in W/(m²·K) and a report expects imperial thermal units. The conversion changes energy-rate, area and temperature-interval factors together.
Thermal conductivity and insulation thickness: separate the material from the wall
An insulation data sheet reports conductivity while a building calculation asks for thermal resistance or a U-value. Converting conductivity to another unit can be useful, but it cannot supply the thickness,.
Centipoise and mPa·s: compare a fluid at the right temperature and shear condition
Two fluid data sheets can report viscosity in different units and at different temperatures. Converting centipoise to Pa·s resolves the unit convention, but a valid comparison still needs the measurement conditions.
Centistokes and oil data: a viscosity grade is not a unit conversion
A lubricant measurement says 46 cSt and another source uses mm²/s. Those units are equivalent, but a viscosity grade belongs to a classification system with its own conditions.
US and Imperial gallons: compare fuel economy on the same basis
US and Imperial gallons differ. Here is how to read the label before converting volume or fuel economy.
Watts and watt-hours: a rate is different from a total
Separate power from energy before converting an appliance rating, battery specification or electricity figure.
Inches, feet and metres: a practical guide to readable dimensions
A practical guide to exact length definitions, sensible rounding and keeping the original measurement beside your conversion.
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