Accuracy classes and tolerances defined by IEC 60751:2008 are:
Class AA ± (0,1+0,0017 * t), ±0,1 °C (0 °C), ±0,27 °C (100 °C), defined on range -50…+250 °C (wire wound resistor), 0…+150 °C (thin film resistor)
Class A ± (0,15+0,002 * t), ±0,15 °C (0 °C), ±0,35 °C (100 °C), defined on range -100…+450 °C (wire wound resistor), -30…+300 °C (thin film resistor)
Class B ± (0,3+0,005 * t), ±0,3 °C (0 °C), ±0,8 °C (100 °C), defined on range -196…+600 °C (wire wound resistor), -500…+500 °C (thin film resistor)
Class C ± (0,6+0,01 * t), not commonly used for industrial measuring circuits.