## Units

Blockpad supports units, and assigning a unit to a number is as easy as typing the unit after it. Blockpad has a set list of built-in units, all of which are listed below.

### Units basics

##### Assign units to a number

To assign a unit to a number, type the unit text after it. For example, `2.3 ft`, `57 kg`, or `391 kPa`

The unit text must match the built-in unit stored in the Blockpad library, but Blockpad will often auto correct to what's intended. The dropdown selection will also help.

##### Composite units

Composite units can be formed using built-in units and regular operators (*, /, and ^). For example, `1 ft/s`, `12 kg*m/s^2`, or `350 lbf*ft`.

##### Convert values

To convert a value to a different unit, the to key word is used. In a formula, type in "to desired unit" after the value you wish to convert. For example, `12 kg*m/s^2 to lbf`, `20 F to C`, or `25000 lbf to kN`.

This can be helpful to simplify the units for the results of some equations. For example, 5 joules divided by 2 seconds might give the answer in J/s, but you want the answer in Watt. ##### Arithmetic

When you do math with numbers and units, Blockpad formulas handle the work for you. Units are auto-converted, cancelled, and multiplied as they need to be.

For example, if you add or subtract numbers with two different length units, like feet and meters, Blockpad will auto-convert to the first unit and give the correct result. Or if you multiply numbers with two different length units, Blockpad auto-converts and multiplies the units appropriately. Dividing two length units gives you a unitless number. Finally, if you try to add or subtract numbers and the units aren't compatibe, like force and length units, then Blockpad tells you there's something wrong. Sometimes numbers need to be unitless for calculations, like when an equation is derived through experimentation. In these cases, the units need to be stripped and added back in order to use units in the rest of the document.

###### Strip units

To strip units from a number value, divide the value by the number one with the unit the value is expected to be.

For example, if the variable length is expected in feet, `length/1 ft` gives the correct unitless number. It doesn't matter what units length has (as long as it's compatible with feet); Blockpad will autoconvert length first, and then the units will cancel out.

To assign units to a unitless number value, multiply that value by the number one with the unit you want it to be.

For example, say the value width is calculated in a way that gives a unitless result, e.g. `width = 1 + 2/sqrt(3)`. To have width in centimeters, multiply that entire formula by 1 cm - `width = (1 + 2/sqrt(3))*1 cm`

###### All together

The effective seating width of a gasket is calculated with the equation `b = 0.5*sqrt(b_0)`, where b_o is expected in inches and the result, b, is also in inches.

To handle this, b_o needs to be divided by 1 inch, and the final equation needs to be multiplied by 1 inch. This way, b_o can have any length unit and Blockpad will automatically convert it to inches, then strip the units. Also, b is now stored in inches, and can be converted to any other compatible unit. ### More on using units

##### foot-inch and other combination units

Foot-inch units (e.g. 5ft 8in or 10ft 2.5in) are an acceptable unit type in Blockpad, along with other units that take a similar form (like degree-minute-second or day-hour-minute). To use these kinds of units, follow the basic layout of number unit number unit number unit, etc.. To convert to this kind of unit, type the units with a space between them after the "to" keyword, or in the specific case of deg-min-sec, type "to dms". For example, `10 m to ft in`, `2.2 day to day hr min`, or `32.34 deg to dms`. Note that this doesn't work for any and all combination of units. `5m 22cm 5mm` doesn't work, and neither does `12kip 250lb`. Only units that are specified in Blockpad as combination units work. Below is a list.

• ft in
• day hr min
• hr min
• min sec
• deg min sec (dms)
##### Temperature difference units

Because conventional temperature scales have different starting points (0 C ≠ 0 F), converting between temperatures and converting between temperature differences require different approaches. So in Blockpad, differences in temperature have units of ΔF or ΔC. Because psia and psig have a similar problem (0 psia ≠ 0 psig), differences in psig are represented with Δpsig units. Note this only applies when psig is explicitly used. Regular psi is a unit and is the typical US customary unit for force/length^2. There is a challenge with converting rpm (revolutions per minute), because it can be considered a unit of frequency (like Hz) or of angular velocity (deg/min or rad/min). This is further complicated by radians, because numbers with radians as a unit can also be considered unitless.

Blockpad handles this problem using context dependent conversions. So converting from rpm, "1 rpm to rad/min" = 2*pi rad/min (angular velocity) and "1 rpm to min^-1" = 1 min^-1 (frequency). Converting from rad/min, "2*pi rad/min to rpm" = 1 rpm (angular velocity) and "2*pi rad/min to min^-1" = 2*pi min^-1 (frequency). Note that this means the original value will be lost if converted between different interpretations. In the example below, x is in rpm; y equals x converted to rad/min; and z equals y converted to min^-1. x ≠ z, even though if you wrote out the equations they would be x = y = z. ##### Pounds - lb, lbf, and lbm

The simple pounds unit (lb) is flexible with conversions to mass or force units. `1 lb to kg` gives 0.454 kg as the result, and `1 lb to N` returns 4.448 N.

Pounds force (lbf) and pounds mass (lbm) are not flexible. Pounds force is only compatible with force units and pounds mass is only compatible with mass units. `1 lbf to kg` will give an error.

##### \$ and usd

Putting a \$ sign in front of a number and putting "usd" behind a number do the same thing. So, `\$12/hr` and `12 usd/hr`

are equivalent.
##### The compatible function

The compatible function checks if two numbers have compatible units. In a sense, it checks if two numbers with units can be added together or if the units of one number could be converted to the units of the other. You can also think of it as checking if the fundamental dimensions are the same (length, mass/length^3, etc). ##### Priority units

You can set priority units for equations and cells so that calculations auto-convert to those units if they are compatible.

###### Set priority units for an equation:
1. Select the equation.
2. Select Value Format in the toolbar.
3. Under Priority Units click Add.
4. Specify the desired units.
5. Click Ok.
6. Repeat steps 3-5 for all units desired.
7. Click Ok to exit Value Format
###### Set priority units for all equations in a file:
1. In the toolbar, select Styles>Manage Styles.
3. For Container select Frame Document.
4. For Object Type select Dynamic Equation.
5. Under Properties select Value Format.
6. In the new window, select Number on the left.
7. Repeat steps 3-5 from above for all units desired.
8. Click Ok to exit Value Format
9. Close out of the Styles window.

### Built-in Units

##### US Units
 ft foot in inch lbf pound force lbm pound mass lb pound (general use) oz ounce (1/16 lb) lb oz pound-ounce kip kip (1000 lbf) psi pound per square inch (lbf/in^2) ksi kip per square inch (kip/in^2) ft in foot-inch (see section above) pcf pound per cubic foot (lbf/ft^3) kcf kip per cubic foot (kip/ft^3) psf pound per square foot (lbf/ft^2) ksf kip per square foot (kip/ft^2) plf pound per linear foot (lbf/ft) klf kip per linear foot (kip/ft) yd yard sy square yard (yd^2) cy cubic yard (yd^3) cfs cubic foot per second (ft^3/s) acre acre (4840 yd^2) F degree Fahrenheit ΔF difference Fahrenheit R Rankine psia absolute pound per square inch (pressure) psig gauge pound per square inch (pressure) Δpsig difference gauge pound per square inch sf square foot (ft^2) cf cubic foot (ft^3) mile mile nautical mile nautical mile mph mile per hour ton US customary ton (2000 lbf) gal US gallon (231 in^3) gpm US gallon per minute Btu British thermal unit (thermochemical definition, 1054.3503 J) slug slug mass unit (1 lbf*s^2/ft) hp mechanical horsepower (550 ft*lbf/s) quart quart (1/4 gal) pint pint (1/2 quart) cup cup (1/4 quart) fl oz fluid ounce (1/8 cup) fl oz FDA FDA fluid ounce (30 mL) Tbsp tablespoon (1/2 fl oz) tsp teaspoon (1/6 fl oz)
##### SI Units
 m meter kg kilogram km kilometer cm centimeter mm millimeter nm nanometer g gram N Newton J Joule Pa Pascal kPa kilopascal MPa megapascal GPa gigapascal bar bar (100,000 Pa) mbar millibar mm Hg millimeters mercury (pressure) atm atmosphere (pressure) K Kelvin C degree Celsius W Watt ΔC difference Celsius kN kilonewton L Liter cL centiliter mL milliliter cc cubic centimeter (cm^3) g0 gravity/ "g's" (1 g0 = 9.807 m/s^2) gravity gravity/ "g's" (1 gravity = 9.807 m/s^2) coulomb Coulomb (electric charge) V Volt A Ampere/Amp Ω Ohm ohm Ohm (same as Ω) H Henry (inductance) farad Farad (capacitance) T Tesla (magnetic induction) Wb Weber (magnetic flux) Mx Maxwell (magnetic flux, 1E-08 Wb) kW kilowatt kJ kilojoule cal "small" calorie (4.184 J) kcal "large" calorie (1000 cal or 4184 J) ppm parts per million ppb parts per billion
##### Time Units
 s second min minute hr hour day day week week mo month year year day hr min sec day-hour-minute-second day hr min day-hour-minute hr min sec hour-minute-second hr min hour-minute min sec minute-second ms millisecond ns nanosecond μs microsecond Hz Hertz (s^-1) rpm rotation per minute
##### Angle Units
 deg degree deg min sec degree-minute-second dms degree-minute-second rad radians rev One revolution (rpm*min)
##### Screen Units
 px virtual pixel (1/96 inch) pt point (1/72 inch)
##### Complex Numbers

Note that terms i and j for complex number are inputed like units, as shown, but they define an imaginary number, rather than a literal number with a unit.

 i the imaginary unit j the imaginary unit (same as i)
##### Currency Units

Note that conversion between currencies is not supported right now.

 usd United States Dollar cad Canadian Dollar eur Euro jpy Japanese Yen gbp Pound sterling aud Australian Dollar chf Swiss Franc cny Chinese Yuan sek Swedish Krona nzd New Zealand Dollar mxn Mexican Peso