Formula & Units app for iPhone and iPad

Formula & Units is an ultimate tool for calculation of complex scientific expressions and convertion of scientific units. Expressions may be comprised of variables and constants, possessing numeric values and sets of units.

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The application interface consists of three custom (A, B, C) value-units expressions and six preset constants, which may be added to the final expression field by pressing the corresponding buttons.

Value-Units Expression contains three fields: value field, numerator (top) units field and denominator (bottom) units field.

Units must be typed exactly as they appear in the provided list in the Help section. Power of unit is typed directly after unit : s2. Metric prefixes or unit prefixes are recognized automatically: mm = 1.0e-3 m, kA = 1000 A. Metric prefix micro- (1e-6), is changed to u. Additional Units can be added upon request through www.volard.wordpress.com.

Example of unit expression as it should appear in numerator or denominator fields: mm2*s*kg*uA-2*MPa-2.

Upon addition or subtraction, unit expressions should be of the same dimensionality! Meters cannot be added to Pascals!!!

Application provides set of widely used physico-chemical constants. Pressing the corresponding constant button adds the value to the final field.
Presets are: Na - Avogadros constant, h - Planck constant, F - Faraday constant, R - gas constant, kB - Boltzmann constant, g - acceleration of gravity, e - elementary charge, Pi - pi constant. (All in SI units)

The final expression is a regular scientific formula consisting of value-units expressions, regular math operations, numbers and functions. Available math functions are provided with buttons-shortcuts.
Dot is used as a decimal point.

Pressing "Calculate" button evaluates final expression. By default, application converts all units to International System of Units (SI), but it is possible to set the required units directly to the final (where result is shown) units fields before calculation, then the result will be adjusted to meet the requirement.

The resulting final expression can be copied to A expression field, by pressing a "A^" top bar button, for further conversion or calculations.

For a simple conversion, type the expression that should be converted to A field and preferred units to the B field.
Special attention should be paid to dimensionality! For example: To change m3 to US Gallon in expression s*kg/m3, type gal-1 to numerator field or gal to denominator field in the B expression. Press convert button to get the final converted result. For conversion numeric value of B expression has no meaning.

Examples can be found at www.volard.wordpress.com.