Accurate reconstruction of past ocean temperatures is of critical importance to paleoclimatology. Carbonate clumped isotope thermometry (“Δ₄₇ ”) is a relatively recent technique based on the strong relationship between calcification temperature and the statistical excess of ¹³C–¹⁸O bonds in carbonates. Its application to foraminifera holds great scientific potential, particularly because Δ₄₇ paleotemperature reconstructions do not require assumptions regarding the ¹⁸O composition of seawater. However there are still relatively few published observations investigating the potential influence of parameters such as salinity or foraminiferal size and species. We present a new calibration data set based on 234 replicate analyses of 9 planktonic and 2 benthic species of foraminifera collected from recent core-top sediments, with calcification temperatures ranging from −2 to 25 °C. We observe a strong relationship between Δ₄₇ values and independent, oxygen-18 estimates of calcification temperatures:

Δ₄₇ = 41.63 × 10³/T² + 0.2056

The formal precision of this regression (± 0.7–1.0 °C at 95 % confidence level) is much smaller than typical analytical errors. Our observations confirm the absence of significant species-specific biases or salinity effects. We also investigate potential foraminifer size effects between 200 and > 560 μm in 6 species, and conclude that all size fractions from a given core-top location and species display statistically undistinguishable Δ₄₇ values. These findings provide a robust foundation for future inter-laboratories comparisons and paleoceanographic applications.