APMCalc app for iPhone and iPad

APMCalc is an arbitrary precision scientific calculator designed from the ground up to provide the most accurate calculations possible. Numbers are stored in a decimal format to represent each number entered exactly. APMCalc algorithms are designed to deliver a set number of significant digits of precision even when approaching function poles and limits. In typical usage, a precision larger than needed is selected and rounding is accomplished prior to number export.

Features:

Precision range from 1 to 1,000,000; no complicated settings — just set and go
Fixed or scientific display format that can be changed on demand
Extremely large numerical range — million digit numbers with exponent range +/- 9223372036854775806
View/Edit windows for handling the large numbers that support cut, copy, paste, select
Paste operations that filter, permitting numbers with grouped digits or surrounded by text to be easily imported
Ongoing calculations can be canceled with a single mouse click
Scientific functions include trigonometry, exponential, logarithms, powers and more
Math constants pi, e, Euler and omega are stored at full precision; golden ratio is computed
Physical constants include the full set of fundamental physical constants from NIST
Conversion between units in the categories of angle, area, energy or work, length, power, pressure, speed, temperature, time, volume, and weight and masses
Reverse Polish Notation (RPN) entry mode
Stable and reliable — catches under/overflows, divide by zero, out of range input and displays informative messages
Unlimited register stack and 26 memory locations — all can be edited
Calculation timing
Retina enabled