Learning
1 tool in the Units area.
Units and Sig Figs Tutor
A teaching tool for unit conversion and significant figures. Factor-label conversion: type a quantity and a target unit (60 mi/h to m/s, 14.7 lbf/in² to kPa, 1 Btu to J) and the tool writes the chain of conversion factors as a textbook does, each factor from NIST SP 811 Appendix B with its exact or rounded value and its source, the unit left after every factor, and the result rounded to the significant figures the input warrants, with the relative-rounding-error reasoning of SP 811 B.7.2. Significant figures: numbers are counted with the rule that applies to every zero, expressions are worked by the addition and multiplication rules, numbers are rounded by the ASTM E29 round-half-to-even method and by round-half-up side by side, and the implied uncertainty (half a unit in the last place) is propagated worst-case and in quadrature for comparison with the rule. Practice: seeded problem sets with hidden answers and a scoring table. The default lines are the three conversions above, the OpenStax Chemistry 2e Section 1.5 examples and the rounding examples of SP 811 B.7.1 and ASTM E29.
1 worked example reproduced, listed on the tool page.