Larger benthic foraminifera (LBF) contribute significantly to the modern reef carbonates. They were also the major producers of carbonate in the shallow marine environments of the Paleogene. It is thus imperative to investigate their potential as a paleotemperature proxy. It is common to calculate past seawater temperatures using trace elements and stable isotope proxies on foraminiferal calcite. The various LBF genera comprise tests with different MgCO$_{3}$% and exhibit vital effects, making it important to carry out genus-specific temperature calibration studies. For the present study, live specimens of Baculogypsina sphaerulata were collected over seven months from reef flats of Akajima (Okinawa, Japan). The whole-shells of B. sphaerulata from each of the seven sampling months were analyzed using ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry) and IRMS (Isotope Ratio Mass Spectrometer) techniques. The relationship between Mg/Ca and $\delta^{18}$O with seawater temperature is established, and thus its potentiality for temperature calibration is discussed. The following proxy-temperature calibrations are proposed in this study: (i) Mg/Ca (mmol/mol) = 0.0267e$^{0.3389T}$ and (ii) $T$ ($^{\circ}$C) = 19.0–2.94 ($\delta^{18}$O$_{f}$−$\delta^{18}$O$_{w}$).

$\bf{Highlights}$

$\bullet$ The geochemical composition of Baculogypsina sphaerulata was studied to understand its potentiality for paleotemperature calibration.

$\bullet$ The regression should be always over the complete range of growth temperatures experienced by the foraminifer for better correlation.

$\bullet$ A genus-specific temperature calibration is important in the case of larger benthic foraminifera.

$\bullet$ The proxy-temperature calibrations for Baculogypsina sphaerulata are proposed in this study.