IIS v10 (but this should be the same also for IIS 7.x)
Quick addition for people which are looking for respective max values
Max for maxAllowedContentLength is: UInt32.MaxValue
4294967295 bytes : ~4GB
Max for maxRequestLength is: Int32.MaxValue 2147483647 bytes : ~2GB
web.config
<?xml version="1.0" encoding="utf-8"?>
<configuration>
<system.web>
<!-- ~ 2GB -->
<httpRuntime maxRequestLength="2147483647" />
</system.web>
<system.webServer>
<security>
<requestFiltering>
<!-- ~ 4GB -->
<requestLimits maxAllowedContentLength="4294967295" />
</requestFiltering>
</security>
</system.webServer>
</configuration>