To Convert: Into: Multiply By: ─────────────────────────── ──────────────────────────── ────────────────── btu (39°F) btu 1.00504 btu (39°F) btu (IST) 1.00439 btu (39°F) btu (mean) 1.00360 btu (39°F) btu (60°F) 1.00473 btu (39°F) joules 1059.67