Fig 1

Fig 2

Unit Selection

First select the From Units and To Units units from the drop-down scrollable lists. To speed the selection, move the cursor to the selections list and enter the first letter of the unit required. This will find the next item in the list starting with that letter. Repeated entry of the same letter cycles through all entries starting with that letter. Entries are in alphabetic order within any subgroups in a category.

Input Numeric Values

The From Value defaults to "1" but you may enter any numeric value. Values may include commas, and may also include exponents in one of the formats shown in the following examples, ( e¹², e⁺¹², or e^-12 ). The exponent may be either lower or upper case ('e' or 'E') but output values use only lower case. This allows values to be copied directly from the converter into the Windows^© calculator. Double clicking in the value field selects the whole of the current value which can then be copied or replaced. To perform a conversion, just move outside the value field, there's no need to press any specific button!

Options

FootRule Converter modules have 2 pairs of radio buttons or icons at the bottom, depending on the formats of converter available for your particular browser. The first two radio buttons have descriptive names of Usage and Definition while the corresponding image buttons on the pictorial converters are:

• Usage (Default) selects a description of the the usual or commonest usage of the unit, and/or the country or countries where it is used. This relates to the "From Unit" for all forms of display.

• Definition is the formal definition of the selected unit and/or reference information. Again, only the "From Unit" is displayed for both the pictorial converter and the non-pictorial converter display.

The second pair of radio buttons have names of 'Scientific' and 'Common' and select the format of numeric calculation and display. The two images buttons are:

• Scientific selects calculation following formal rules of accuracy based on significant digits, including the number of digits in the user entered value. The result values are displayed in scientific format with exponents. See the page on Accuracy for more detail.

  NOTE! If Scientific calculation is selected, the result or "To" value will have the same number of digits as the user entered value. For example, 1 meter will be converted to 1 yard, 1.0 meters will be converted to 1.1 yards, 1.00 meters = 1.09 yards, 1.000 meters = 1.094 yards and so on.

• Common (Default) selects calculation based on up to 15 digit accuracy. Values greater than 10¹³ or smaller than 10^-6 are displayed in scientific format for ease of reading. For example, 1 meter is converted to 1.093 613 298 337 71 yards, 1 000 000 000 000 000 meters converted to 1.093 613 298 337 71 e¹⁴ yards and 0.000 000 1 meters converted to 1.093 613 298 337 71 e^-7 yards.

Result Format

In both cases, resultant values are displayed in the format recommended by the section titled "#16 Digit Spacing" of the NIST reference on SI Unit rules and style conventions.

Reciprocal/Reverse Conversions

Reciprocal or reverse conversions can also easily be found. For example, having found the conversion from meters to yards, to find the reverse conversion from yards to meters, just enter a value into the From Value field then simply move the cursor elsewhere. The system automatically switches the From and To units and performs the necessary calculations.

Category Descriptions

Clicking on the title of a category displays a table of descriptive information about that category such as the definition of the category and the base units in the S.I. and Imperial systems.

Other Converters

FootRule.com includes many other converters and links to converters on other sites, each of which will operate in their own way and will usually be self explanatory or include appropriate instructions.