Investments in information technology are hard to assess due to various reasons, such as lack of easy-to-use methods and appropriate input data. The aim of the paper is to reduce the uncertainty of investment assessments and investment follow up. This is done by addressing the problem with lack of quantified data. A simple method is proposed for transferring intangible and qualitative data into tangible and quantifiable data. The method is a step by step process from identify-ing benefits to finding appropriate values for estimating the magnitude of the ben-efits, and to further quantify the benefits using available data. The values could thereafter be used in traditional economic investment assessment models such as the payback period or net present value method. The proposed method is illustrat-ed using an investment in a computerised maintenance management system as an example.