Many applications require determining the number of cells or particles inside of a sample. This can be done by weighting the dry mass of cells/particles and afterwards calculating the number concentration in the solution. However this only gives an estimate of the concentration. Alternatively optical methods like haemocytometers, which are labor intensive or automated cell counters, which rely on well-defined samples and work in only narrow concertation ranges, can be used. Fluorescent assisted cell sorting (FACS) is a reliable option, which requires expensive, specialized equipment. Here we present a simple method to count cells and microparticles, based on a microfluidic well array device. For this the sample is split up into 23.400 picoliter sized microwells. Afterwards the device is imaged using a conventional bright field microscope. Wells containing one or more particles/ cells can be identified through their deviating light intensity by a custom written computer program. Finally concentrations are calculated through the fraction of occupied wells by Poisson statistics. The average number of cells/ particles per well can be calculated and the concentration calculated from the well volume. Using the approach shown here cells and particles over a concentration range of 4 orders of magnitude can be counted in a fast, simple and cost effective manner. This is demonstrated using two different kinds of microparticles (5µm and 10µm diameter) as well as HeLa cells.