APEX can create "Percentage Bars" within a report. They're probably a lot of 3rd party tools you can use for fancy percentage bars, however if you want a basic display to the user here's a quick way to do it. Click here for a demo.
1- Create your report In this report we're using the employees percentage of salary within their department
SELECT e.ename, e.job, d.dname, e.sal, ROUND (e.sal / SUM (e.sal) OVER (PARTITION BY e.deptno) * 100, 0) pct_dep_sal, ROUND (e.sal / SUM (e.sal) OVER (PARTITION BY e.deptno) * 100, 0) bar FROM emp e, dept d WHERE e.deptno = d.deptno
2- Add Percentage Bar for the "bar" column
- In the Reports Attributes section, click on the "Bar" column attributes
- Under Number/Date formatting enter the following:
PCT_GRAPH:<Hex background color>:<Hex foreground color>:<Bar width in pixels>