To develop a quantitative T1-mapping-based synthetic inversion recovery (IR_synth) approach to calculate the optimal inversion time (TI₀) for late gadolinium enhancement (LGE) imaging. Prospectively enrolled patients (n = 130, 58 ± 16 years) underwent cardiac MRI on a 1.5T system including Look-Locker TI-scout (LL), modified LL IR (MOLLI)-based T1-mapping, and LGE acquisitions. Patients were randomized into two groups: LL group (TI-scout followed T1-mapping) or MOLLI group (T1-mapping followed TI-scout). In both groups, the second acquisition was used to determine the TI₀ for LGE. IR_synth images were generated from T1-maps between TI = 200–400 ms in 5 ms increments. Image quality was rated on a 3-point scale and the remote/background signal intensity ratio (SIR) was calculated. In the LL group (n = 53), the TI-scout-based TI₀ was significantly shorter compared to IR_synth [230 ms (219–242) vs. 280 ms (263–297), P < 0.0001]. The TI₀ used for LGE was set 30–40 ms longer [261 ms (247–276), P < 0.0001] than the TI-scout-based TI₀, resulting in a TI₀ ~ 20 ms shorter than what was obtained by IR_synth (P = 0.0156). In the MOLLI group (n = 63), IR_synth-based TI₀ was significantly longer than the TI-scout-based TI₀ [298 ms (262–334) vs. 242 ms (217–267), P = 0.0313]. The quality of myocardial nulling was rated higher [2.4 (2.2–2.5) vs. 2.0 (1.8–2.1), P = 0.0042] and the remote/background SIR was found to be more optimal (1.6 [1.1–2.1] vs. 2.6 [1.8–3.3], P = 0.0256) in the MOLLI group. T1-based IR_synth selects TI₀ for LGE more accurately than conventional TI-scout imaging. IR_synth improves TI₀ selection by providing excellent visualization of the representative image contrast for LGE images, reducing operator dependence in LGE acquisition.