Researchers from Finland's Aalto University, the University of Cambridge in the UK and Switzerland's ETH Zürich found that people type about 70% as fast on mobile devices as on QWERTY keyboards.
The study looked at speed and accuracy data from a typing test taken by 37,000 volunteers in 160 countries.
The so-called "typing gap" is closing as people become less skilled at using full keyboards and better at using mobile devices.
Increasing use of mobile devices may explain some increase in speed, but features such as auto-correct also improve performance.
One person was able to hit a remarkable 85 words per minute on a mobile device, while the average performance among volunteers was around 36 words per minute.
Using both thumbs proved to be the best way to achieve high typing speeds on mobile devices. Some 74% of users in the survey reported doing so.
"We were amazed to see that users typing with two thumbs achieved 38 words per minute on average, which is only about 25% slower than the typing speeds we observed in a similar large-scale study of physical keyboards," study co-author Anna Feit, a researcher at ETH Zürich, said in a statement.
"While one can type much faster on a physical keyboard, up to 100 wpm, the proportion of people who actually reach that is decreasing. Most people achieve between 35-65 WPM."
Auto-correction was found to increase typing speeds on mobile devices but word prediction didn't, as the time spent thinking about choosing a word outweighed its typing time.
Researchers also found a strong generational effect, with those aged 10-19 an average of 10 words per minute faster on mobile devices than those in their 40s.
"We are seeing a young generation that has always used touchscreen devices, and the difference to older generations that may have used devices longer, but different types, is staggering," said Antti Oulasvirta, an academic at Aalto University.
The data was gathered from around the world, but most of the volunteers were women in their early 20s. On average the volunteers spent around six hours a day using a mobile device, and about 50% of the participants came from the US.
The findings will be presented Wednesday as part of the 21st International Conference on Human-Computer Interaction with Mobile Devices and Services (MobileHCI), in Taipei.