Understanding Execution Governors and Limits

Total number of SOQL queries issued1	100
Total number of SOQL queries issued for Batch Apex and future methods1	200
Total number of records retrieved by SOQL queries	50,000
Total number of records retrieved by Database.getQueryLocator	10,000
Total number of SOSL queries issued	20
Total number of records retrieved by a single SOSL query	2000
Total number of DML statements issued2	150
Total number of records processed as a result of DML statements, Approval.process, or database.emptyRecycleBin	10,000
Total number of executed code statements	200,000
Total number of executed code statements for Batch Apex and future methods	1,000,000
Total heap size3	6 MB
Total heap size for Batch Apex and future methods	12 MB
Total stack depth for any Apex invocation that recursively fires triggers due to insert, update, or delete statements4	16
For loop list batch size	200
Total number of callouts (HTTP requests or Web services calls) in a request	10
Maximum timeout for all callouts (HTTP requests or Web services calls) in a request	120 seconds
Default timeout of callouts (HTTP requests or Web services calls) in a request	10 seconds
Total number of methods with the future annotation allowed per Apex invocation5	10
Maximum size of callout request or response (HTTP request or Web services call)6	3 MB
Total number of sendEmail methods allowed	10
Total number of describes allowed7	100
Total number of classes that can be scheduled concurrently	100
Total number of test classes that can be queued per a 24-hour period8	The greater of 500 or 10 multiplied by the number of test classes in the organization