Early Islamic chronicles report specific casualty figures for battles such as Yamama, but modern historians of the early Islamic conquests regard those numbers as products of a later, formulaic chronicle tradition rather than contemporary counts, so no synthesis treats them as a reliable basis for a total.
What would resolve this A source critical study weighing which, if any, of the early chronicle casualty figures for the Ridda Wars can be treated as historically reliable, or an archaeological approach to Arabian population loss in the period.
OpenEarly Islamic history, source criticism.Hugh Kennedy, The Great Arab Conquests: How the Spread of Islam Changed the World We Live In