Accurately no, logical estimates yes. Free black males eligable for services by age in 1860 about 10,000- male slaves by 1864 legislation about 40,000. My estimation- combined total at its peak 15,000-20,000 nation wide (that is service to the military directly). Black persons in civil service working to provide necessary products and work to the States and Confederacy would weaken any direct military service. Private needs to produce cotton, etc.- to fund the war, still took a priority for most of the period. Still a small percentage compared to the millions of Blacks in the South.