The neat online questionnaire takes about five minutes to complete and only works for people aged 55 or over, but is 83 per cent accurate, the scientists say.
Various other online calculators exist on the web, but few have robust scientific data behind them.
"What sets this dementia risk calculator apart is that you don't need to visit a doctor for any tests," said Dr Stacey Fisher, the lead author of the study who performed the research largely while she was a PhD student at Ottawa Hospital.
"People already have all the information they need to complete the calculator in the comfort of their home."
The questions asked correspond directly to the data gathered by the scientists in their Dementia Population Risk Tool (DemPoRT).
Factors it takes into account include age, smoking status and lifetime exposure, alcohol consumption, physical activity, stress, diet, sense of belonging, ethnicity, immigration status, socioeconomic status of the neighbourhood, education, activities where assistance is needed, marital status, number of languages spoken, and health conditions.
It gives a person their relative level of risk, as well as picking out aspects of their life where they can make changes to reduce their risk further.
"This tool will give people who fill it out clues to what they can do to reduce their personal risk of dementia," said Dr Peter Tanuseputro, senior author of the study.
He added: "The Covid-19 pandemic has made it clear that socio-demographic variables like ethnicity and neighbourhood play a major role in our health. It was important to include those variables in the tool so policy makers can understand how different populations are impacted by dementia, and help ensure that any prevention strategies are equitable."
The website hosting the dementia online calculator has various other health-related quizzes, including "how long will I live?" and "what's my risk of having a heart attack or stroke?"
