The Laptev Sea is a shallow marginal ocean and has a strong contribution to the production of sea ice in the Arctic Ocean. In addition to sea ice formed during the autumn freeze-up a certain amount is produced in polynyas along the fast-ice edge throughout the winter. A reasonable quantification of ice volume produced by polynya opening events based on in situ thickness data is still pending. Here we present an estimation of sea-ice volume produced in polynyas in the south eastern Laptev Sea for the period of January–April 2008 based on helicopter electromagnetic (HEM) sea-ice thickness measurements and synthetic aperture radar (SAR) satellite images. SAR images, taken on a daily interval, were used to track ice areas of equal age from their origin to the moment when we measured their thickness with the HEM instrument. In this way we created a sea-ice age chart for the south eastern Laptev Sea in April and linked this information to thickness results from HEM measurements. In total 570 km of HEM ice-thickness data is available with modal thicknesses of between 0.1 and 1.7 m. In order to expand thickness information along single profiles to areal information, we assume that modal thicknesses are representative for areas of the same age. Finally, these results can be used to validate ice-thickness productions rates obtained from model studies which used for example the NAOSIM of FESOM code.