[1RM](http://michaelgalloy.com/wp-content/uploads/2006/06/1RM.wdgt.zip) is a Mac OS X Dashboard widget that calculates your maximum possible lift (1RM, "one-rep max") given the number of times a submaximal lift weight was lifted. For convenience, it also lists simple percentages of the 1RM calculated and a suggest number of reps for that weight.
The formula used to calculate the one-rep maximum is:
1RM = wt / (0.997568 - 0.0248505 * r)
where `wt` is the weight lifted `r` times.
Installation is straightforward. Here are Apple's instructions:
>Mac OS X 10.4 Tiger is required. If you're using Safari, click the
>download link. When the widget download is complete, show
>Dashboard, click the Plus sign to display the Widget Bar and click
>the widget's icon in the Widget Bar to open it. If you're using a
>browser other than Safari, click the download link. When the
>widget download is complete, unarchive it and place it in
>`/Library/Widgets/` in your home folder. show Dashboard, click the
>Plus sign to display the Widget Bar and click the widget's icon in
>the Widget Bar to open it.
### Version history
Version 1.3, March 2009 ([download](http://michaelgalloy.com/wp-content/uploads/2009/03/1RM.wdgt.zip))
: Enforced limits of 0-10 reps.
Version 1.2, January 2009 ([download](http://michaelgalloy.com/wp-content/uploads/2009/01/1RM.wdgt.zip))
: Tweaked formula to ensure 1RM is equal to weight when reps is 1; upgraded to fully Leopard-compatible (cosmetic differences).
Version 1.1, June 2006 ([download](http://michaelgalloy.com/wp-content/uploads/2006/06/1RM.wdgt.zip))
: Cleaned up interface.
Version 1.0, May 2006 ([download](http://michaelgalloy.com/wp-content/uploads/2006/05/1RM.wdgt.zip))
: Original version.