The assessment of language lateralisation with fMRI using the laterality index is limited by the dependence of the results on the chosen activation threshold. To overcome this limitation, different threshold-independent laterality index calculations have been introduced. This work proposes a new method and evaluates how it performs in comparison with three previously reported methods. The methods were evaluated on fifteen healthy subjects who performed picture naming, verb generation, and word fluency tasks. The novel method is simple to implement, fast, robust, reproducible, and compares well with the others in differentiating strong from weak lateralisation on both hemispheric and regional scales.