In making this calculation it is important to understand that numbers, in beekeeping, are not set in concrete. A good example of this is found in the standard developmental times given for workers (21 days), queens (16 days), and drones (24 days). These days can vary by + or – from 1 to 2 days depending on such factors as nutrition, temperature, and subspecies of bee (Africanized bees develop in a lesser amount of time thus contributing to their displacement of European bees when entering new territory). The number obtained in this calculation is a rough estimate of the egg laying rate, but still a good number to glean information from.
To calculate the egg laying rate you will need a ruler and the usage of some simple math.
1) Measure the length and width of capped worker brood on one side of a brood comb. If you measure a 5″x6″ area this gives 30 sq. in. for that side. Do the same for the other side and all other combs with capped brood. Measure the capped drone brood seperately
2) Add together the square inch totals of capped worker brood to give a grand total of capped brood. Do the same for any drone brood.
3) Take the total sq. in. of capped worker brood x 25 (# of worker cells/sq. in.). Take the total sq. in. of drone brood x 16 (# of drone cells/sq. in.)
4) Divide the total capped worker brood by 12 (# of days worker brood is capped). Divide the capped drone brood by 15 (# of days drone brood is capped). Add these together to get the approximate daily egg laying rate. You can increase the accuracy of this result by counting and eliminating from the total any uncapped cells within the measurement area.
As a simple example; I have no drone brood and come up with a grand total of 720 sq. in. of capped worker brood. This equals 18,000 capped worker cells (720 x 25 = 18,000). If I divide this total by 12 I come up with a daily egg laying rate of 1,500/day. (18,000/12=1,500). This is considered by many authorities to be a good laying rate; reports of double that number can be found. You can use this number to predict the emerging workers in the next 12 days, estimate the # of workers being given in transfering a brood frame to another hive, etc.