Table 1. Resonator EPR signal characteristics calculated and measured using a power saturation measurement of a lithium phthalocyanine point sample.

Dimensions of the resonators and further experimental details are provided in the Supplementary Materials.

Geometry	Unsat. signal		Sat. signal		Eff. η	Q0-value Meas.	ηQ0
	Calc.	Meas.	Calc.	Meas.
Bruker MD5W1	1.0	1.0	1.0	1.0	6.12 × 10−6	6650	1.0
Bruker MS3	1.5	1.2	1.0	1.0	79.6 × 10−6	600	1.17
PMR RO6010LM	4.4	1.2	0.9	1.2	4.63 × 10−3	61	6.94
PMR sapphire	18.6	13.3	3.9	3.8	4.63 × 10−3	181	20.59
Microhelix	35.7	28.2	6.1	5.7	6.63 × 10−3	220	35.84