Smear Platelet Estimate Calculator

A manual estimate of the platelet count from a peripheral blood smear correlates the number of platelets per oil immersion field (1000×, high-power field) with the automated count. The most common convention multiplies the average platelets per field by 20,000, so that roughly 8-20 platelets per field correspond to a normal count (about 150,000-400,000/µL) and fewer than 5 per field suggests significant thrombocytopenia. The estimate is useful when an automated count is unavailable or unreliable (for example with platelet clumping or giant platelets).