OligoCalc is an online computational tool developed by Warren A. Kibbe for calculating various properties of DNA and RNA oligonucleotides, including molecular weight, solution concentration, melting temperature, estimated absorbance coefficients, inter-molecular self-complementarity, and intra-molecular hairpin loop formation. The tool has a user-friendly interface, allowing users to input sequences and select options such as single- or double-stranded molecules, chemical modifications, and salt and primer concentrations. Since its launch in 1997, OligoCalc has been accessed over 900,000 times from nearly 200,000 distinct hosts. It provides three common methods for calculating melting temperatures, including a nearest-neighbor thermodynamic model. The tool is available at http://basic.northwestern.edu/biotools/OligoCalc.html, with additional resources and statistics accessible through this link. OligoCalc supports a wide range of applications, from molecular biology to genomic and array technologies, and is compatible with various web browsers.OligoCalc is an online computational tool developed by Warren A. Kibbe for calculating various properties of DNA and RNA oligonucleotides, including molecular weight, solution concentration, melting temperature, estimated absorbance coefficients, inter-molecular self-complementarity, and intra-molecular hairpin loop formation. The tool has a user-friendly interface, allowing users to input sequences and select options such as single- or double-stranded molecules, chemical modifications, and salt and primer concentrations. Since its launch in 1997, OligoCalc has been accessed over 900,000 times from nearly 200,000 distinct hosts. It provides three common methods for calculating melting temperatures, including a nearest-neighbor thermodynamic model. The tool is available at http://basic.northwestern.edu/biotools/OligoCalc.html, with additional resources and statistics accessible through this link. OligoCalc supports a wide range of applications, from molecular biology to genomic and array technologies, and is compatible with various web browsers.