Chlorine-36 (36Cl) is currently the only in situ cosmogenic nuclide applicable in carbonates, Ca- and K-rich feldspars and aphyric silicate rocks. Because the production reactions of 36Cl are more numerous and complex than those of other cosmogenic nuclides (e.g. 10Be, 3He), comprehensive and user-friendly calculators are essential for routine application of 36Cl to Earth surface research questions. However, the existing, commonly used calculators are affected by several drawbacks, such as oversimplification of the muon production model, or the absence of choice regarding production rate parameters. Here, we present the novel 36Cl exposure age calculation tool in development, “CREp 36Cl dev”, which we have implemented as a new functionality in the existing cosmic-ray-exposure program CREp for 10Be and 3He exposure ages. Taking advantage of the most recently developed scaling, muon and low-energy neutron models, “CREp 36Cl dev” allows calculating surface exposure ages, providing several choices between scaling and muon models and production parameters. “CREp 36Cl dev” can be accessed at https://crep-dev.otelo.univ-lorraine.fr/#/.