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can be saved for later use. It is also possible to change units and decimals on a workshect without saving a custom units set; changes to units and decimals are always included in saved worksheets and runs. In addition, BehavePlus includes a helpful Units converter tool (Section 5.5). Specifics of units and decimal features are described in the following sections. Because of issues that can arise due to round off and unit conversions, some basic chang- es have been made to decimal handling in Version 5.0. We recognize that there is some awkward behavior in decimal display resulting from program design decisions that were made years ago, but this cannot be changed without a major redesign. BehavePlus calculations are performed in what we call native units, the units of the pub- lication that describes the mathematical model. This explains some of the behavior that might seem odd. For example, Rothermel's model uses fuel load in lb/ft'- and fuel model parameters are stored in those units. The default display units are tons/ac. The 1-h fuel load for fuel model 5 is stored internally as 0.046 lb/ft', which is equivalent to 1.00188 ton/ac. Most users will use the same units set (our English or metric or their custom set) for all of their runs and will not switch back and forth between units sets. We have attempted to make the units and decimal handling easiest for the largest user group. 5.1 Input Variable Decimals Prior to Version 5.0, decimal display of input variables was determined by the setting in the English, metric, or custom units set. Because the program uses values that are visible on the worksheet to make the calculations, there were occasional problems with round off and misinterpretation. Decimal display of input variables is now determined by the values entered by the user. The greatest number of decimal places (precision) entered for a vari- able determines the decimal display on output tables. In the example in Figure 22, one of the values entered for dead fuel moisture was 9.25% (two decimal places) so all of the dead fuel moisture values on the output table are shown with two decimal places. (This example simply demonstrates the way that the program handles decimal display; a mois- ture value to that precision is not meaningful.) Similarly, a value of 6.5 mi/h was entered for midflame wind speed, so all of the wind values are shown on the table to one decimal place. 30 USDA Forest Service Gen. Tech. Rep. RMRS-GTR-249.2010