There are literally dozens of on-line calculators available for individuals and companies to calculate their own carbon footprint. We do not evaluate the quality of such calculators. It is important that you choose a calculator that takes into account the regional conditions of where you live (e.g. the fuel mix used to produce electricity in your area). Some calculators are very detailed and you will need your utility data read, others use estimates and are easier to use but less accurate. We recommend you google 'best carbon calculators' and then use several of them and compare the results you get.
The largest discrepancies in results can be found in airtravel emissions calculators. This is because some emissions calculators take into account only the CO2 emissions from aviation whereas others also estimate the non-CO2 warming effects from aviation. To learn more about this topic, please read our aviation section of this website.
And remember, before you offset, minimize your own emissions and advocate for stringent climate protection policies. Offsets alone will not save the climate.