What is the resistance of a Pt100 at 0 °C?

Exactly 100.00 Ω by definition — that is what the “100” in Pt100 means. A Pt1000 is 1000.00 Ω at 0 °C. Both use the same temperature coefficient, α = 0.003851 °C⁻¹, so a Pt1000 reads exactly ten times the Pt100 value at every temperature.

What equation does this table use?

The Callendar–Van Dusen equation from IEC 60751:2008. For t ≥ 0 °C, R(t) = R₀(1 + At + Bt²); below 0 °C a third term is added, R(t) = R₀(1 + At + Bt² + C(t − 100)t³), with A = 3.9083 × 10⁻³ °C⁻¹, B = −5.775 × 10⁻⁷ °C⁻² and C = −4.183 × 10⁻¹² °C⁻⁴.

How do I convert a resistance back to a temperature?

Above 0 °C the quadratic inverts in closed form: t = (−A + √(A² − 4B(1 − R/R₀))) / 2B. Below 0 °C the quartic has no simple inverse and is solved numerically or from a lookup table. The reverse table on this page and the Pt100 calculator both invert the equation itself, so they agree with the forward table exactly.

What is the difference between Class A and Class B?

They are tolerance bands on how far a sensor may deviate from this table. Class A is ±(0.15 + 0.002|t|) °C over −100 to +450 °C; Class B is ±(0.30 + 0.005|t|) °C over −196 to +600 °C. At 100 °C that is ±0.35 °C versus ±0.80 °C. Tolerance is not uncertainty: an uncalibrated Class A sensor still needs a calibration and an uncertainty budget before you can claim either number.

Is a Pt100 or a Pt1000 better?

A Pt1000 has ten times the sensitivity (about 3.85 Ω/°C against 0.385 Ω/°C near 0 °C), so lead-resistance and self-heating errors matter ten times less as a fraction of the reading — useful for two-wire and long-cable installations. A Pt100 remains the norm for reference-grade four-wire work, where lead resistance is cancelled anyway and lower self-heating power matters.

Why does my sensor read 100.2 Ω in an ice bath?

An ice point should read 100.00 Ω. 100.2 Ω is +0.51 °C, which is outside Class A (±0.15 °C at 0 °C) and Class B (±0.30 °C). Check the ice bath itself first — a poorly packed bath sits above 0 °C — then lead resistance if the sensor is wired two-wire, then suspect drift or strain in the element.

Reference data

Pt100 resistance table

Resistance against temperature for Pt100 and Pt1000 sensors from -200 °C to 850 °C, computed from the IEC 60751 Callendar–Van Dusen equation rather than transcribed — with the sensitivity and the tolerance limits you need to judge a reading.

Convert a specific value Standards index

The short answer

A Pt100 reads 100.00 Ω at 0 °C and roughly 0.385 Ω per °C near the ice point, falling to about 0.33 Ω/°C at 600 °C because the characteristic is slightly non-linear. A Pt1000 is the same curve multiplied by ten. The table below is the standard's own equation evaluated at every 10 °C; the sensitivity column tells you how much a 0.01 Ω measurement error is worth in °C at that point.

Resistance and tolerance, −200 to 850 °C

Tolerance columns are the class limits at that temperature, in °C. A dash means the class is not defined there by IEC 60751.

Pt100 and Pt1000 resistance, sensitivity and tolerance class limits from -200 to 850 °C
t (°C)	Pt100 (Ω)	Pt1000 (Ω)	dR/dt (Ω/°C)	Class AA (±°C)	Class A (±°C)	Class B (±°C)
-200	18.52	185.2	0.4323	—	—	—
-190	22.83	228.3	0.4288	—	—	1.25
-180	27.10	271.0	0.4254	—	—	1.20
-170	31.34	313.4	0.4223	—	—	1.15
-160	35.54	355.4	0.4194	—	—	1.10
-150	39.72	397.2	0.4166	—	—	1.05
-140	43.88	438.8	0.4141	—	—	1.00
-130	48.00	480.0	0.4116	—	—	0.95
-120	52.11	521.1	0.4094	—	—	0.90
-110	56.19	561.9	0.4073	—	—	0.85
-100	60.26	602.6	0.4053	—	0.35	0.80
-90	64.30	643.0	0.4035	—	0.33	0.75
-80	68.33	683.3	0.4017	—	0.31	0.70
-70	72.33	723.3	0.4001	—	0.29	0.65
-60	76.33	763.3	0.3986	—	0.27	0.60
-50	80.31	803.1	0.3971	0.18	0.25	0.55
-40	84.27	842.7	0.3958	0.17	0.23	0.50
-30	88.22	882.2	0.3945	0.15	0.21	0.45
-20	92.16	921.6	0.3932	0.13	0.19	0.40
-10	96.09	960.9	0.3920	0.12	0.17	0.35
0	100.00	1000.0	0.3908	0.10	0.15	0.30
10	103.90	1039.0	0.3897	0.12	0.17	0.35
20	107.79	1077.9	0.3885	0.13	0.19	0.40
30	111.67	1116.7	0.3874	0.15	0.21	0.45
40	115.54	1155.4	0.3862	0.17	0.23	0.50
50	119.40	1194.0	0.3851	0.18	0.25	0.55
60	123.24	1232.4	0.3839	0.20	0.27	0.60
70	127.08	1270.8	0.3827	0.22	0.29	0.65
80	130.90	1309.0	0.3816	0.24	0.31	0.70
90	134.71	1347.1	0.3804	0.25	0.33	0.75
100	138.51	1385.1	0.3793	0.27	0.35	0.80
110	142.29	1422.9	0.3781	0.29	0.37	0.85
120	146.07	1460.7	0.3770	0.30	0.39	0.90
130	149.83	1498.3	0.3758	0.32	0.41	0.95
140	153.58	1535.8	0.3747	0.34	0.43	1.00
150	157.33	1573.3	0.3735	0.35	0.45	1.05
160	161.05	1610.5	0.3723	0.37	0.47	1.10
170	164.77	1647.7	0.3712	0.39	0.49	1.15
180	168.48	1684.8	0.3700	0.41	0.51	1.20
190	172.17	1721.7	0.3689	0.42	0.53	1.25
200	175.86	1758.6	0.3677	0.44	0.55	1.30
210	179.53	1795.3	0.3666	0.46	0.57	1.35
220	183.19	1831.9	0.3654	0.47	0.59	1.40
230	186.84	1868.4	0.3643	0.49	0.61	1.45
240	190.47	1904.7	0.3631	0.51	0.63	1.50
250	194.10	1941.0	0.3620	0.53	0.65	1.55
260	197.71	1977.1	0.3608	—	0.67	1.60
270	201.31	2013.1	0.3596	—	0.69	1.65
280	204.90	2049.0	0.3585	—	0.71	1.70
290	208.48	2084.8	0.3573	—	0.73	1.75
300	212.05	2120.5	0.3562	—	0.75	1.80
310	215.61	2156.1	0.3550	—	0.77	1.85
320	219.15	2191.5	0.3539	—	0.79	1.90
330	222.68	2226.8	0.3527	—	0.81	1.95
340	226.21	2262.1	0.3516	—	0.83	2.00
350	229.72	2297.2	0.3504	—	0.85	2.05
360	233.21	2332.1	0.3492	—	0.87	2.10
370	236.70	2367.0	0.3481	—	0.89	2.15
380	240.18	2401.8	0.3469	—	0.91	2.20
390	243.64	2436.4	0.3458	—	0.93	2.25
400	247.09	2470.9	0.3446	—	0.95	2.30
410	250.53	2505.3	0.3435	—	0.97	2.35
420	253.96	2539.6	0.3423	—	0.99	2.40
430	257.38	2573.8	0.3412	—	1.01	2.45
440	260.78	2607.8	0.3400	—	1.03	2.50
450	264.18	2641.8	0.3389	—	1.05	2.55
460	267.56	2675.6	0.3377	—	—	2.60
470	270.93	2709.3	0.3365	—	—	2.65
480	274.29	2742.9	0.3354	—	—	2.70
490	277.64	2776.4	0.3342	—	—	2.75
500	280.98	2809.8	0.3331	—	—	2.80
510	284.30	2843.0	0.3319	—	—	2.85
520	287.62	2876.2	0.3308	—	—	2.90
530	290.92	2909.2	0.3296	—	—	2.95
540	294.21	2942.1	0.3285	—	—	3.00
550	297.49	2974.9	0.3273	—	—	3.05
560	300.75	3007.5	0.3261	—	—	3.10
570	304.01	3040.1	0.3250	—	—	3.15
580	307.25	3072.5	0.3238	—	—	3.20
590	310.49	3104.9	0.3227	—	—	3.25
600	313.71	3137.1	0.3215	—	—	3.30
610	316.92	3169.2	0.3204	—	—	3.35
620	320.12	3201.2	0.3192	—	—	3.40
630	323.30	3233.0	0.3181	—	—	3.45
640	326.48	3264.8	0.3169	—	—	3.50
650	329.64	3296.4	0.3158	—	—	3.55
660	332.79	3327.9	0.3146	—	—	3.60
670	335.93	3359.3	0.3134	—	—	3.65
680	339.06	3390.6	0.3123	—	—	3.70
690	342.18	3421.8	0.3111	—	—	3.75
700	345.28	3452.8	0.3100	—	—	3.80
710	348.38	3483.8	0.3088	—	—	3.85
720	351.46	3514.6	0.3077	—	—	3.90
730	354.53	3545.3	0.3065	—	—	3.95
740	357.59	3575.9	0.3054	—	—	4.00
750	360.64	3606.4	0.3042	—	—	4.05
760	363.67	3636.7	0.3030	—	—	4.10
770	366.70	3667.0	0.3019	—	—	4.15
780	369.71	3697.1	0.3007	—	—	4.20
790	372.71	3727.1	0.2996	—	—	4.25
800	375.70	3757.0	0.2984	—	—	4.30
810	378.68	3786.8	0.2973	—	—	4.35
820	381.65	3816.5	0.2961	—	—	4.40
830	384.60	3846.0	0.2950	—	—	4.45
840	387.55	3875.5	0.2938	—	—	4.50
850	390.48	3904.8	0.2927	—	—	4.55

Resistance to temperature

Common meter readings inverted back to temperature for a Pt100. Divide a Pt1000 reading by ten first.

Measured (Ω)	Temperature (°C)
80.00	-50.77
90.00	-25.49
96.00	-10.22
100.00	0.00
100.39	1.00
103.90	9.99
107.79	19.99
110.00	25.68
119.40	50.01
138.51	100.01
157.33	150.01
175.86	200.01
200.00	266.35
247.09	399.99
280.00	497.07

Using the table honestly

The table is the nominal sensor. A real element sits somewhere inside its tolerance band, and that band is a manufacturing limit, not a measurement uncertainty.
To claim an uncertainty you need a calibration of that sensor with that instrument — build the budget with the uncertainty budget calculator.
Two-wire wiring adds the lead resistance straight onto the reading: 1 Ω of cable is about 2.6 °C on a Pt100 and 0.26 °C on a Pt1000.
Self-heating: the sense current dissipates I²R in the element. 1 mA in a Pt100 at 0 °C is 0.1 mW, which is small in stirred liquid and not small in still air.
Deciding whether a reading passes a tolerance needs a stated decision rule — see the guard band calculator.

Frequently asked questions

What is the resistance of a Pt100 at 0 °C?: Exactly 100.00 Ω by definition — that is what the “100” in Pt100 means. A Pt1000 is 1000.00 Ω at 0 °C. Both use the same temperature coefficient, α = 0.003851 °C⁻¹, so a Pt1000 reads exactly ten times the Pt100 value at every temperature.
What equation does this table use?: The Callendar–Van Dusen equation from IEC 60751:2008. For t ≥ 0 °C, R(t) = R₀(1 + At + Bt²); below 0 °C a third term is added, R(t) = R₀(1 + At + Bt² + C(t − 100)t³), with A = 3.9083 × 10⁻³ °C⁻¹, B = −5.775 × 10⁻⁷ °C⁻² and C = −4.183 × 10⁻¹² °C⁻⁴.
How do I convert a resistance back to a temperature?: Above 0 °C the quadratic inverts in closed form: t = (−A + √(A² − 4B(1 − R/R₀))) / 2B. Below 0 °C the quartic has no simple inverse and is solved numerically or from a lookup table. The reverse table on this page and the Pt100 calculator both invert the equation itself, so they agree with the forward table exactly.
What is the difference between Class A and Class B?: They are tolerance bands on how far a sensor may deviate from this table. Class A is ±(0.15 + 0.002|t|) °C over −100 to +450 °C; Class B is ±(0.30 + 0.005|t|) °C over −196 to +600 °C. At 100 °C that is ±0.35 °C versus ±0.80 °C. Tolerance is not uncertainty: an uncalibrated Class A sensor still needs a calibration and an uncertainty budget before you can claim either number.
Is a Pt100 or a Pt1000 better?: A Pt1000 has ten times the sensitivity (about 3.85 Ω/°C against 0.385 Ω/°C near 0 °C), so lead-resistance and self-heating errors matter ten times less as a fraction of the reading — useful for two-wire and long-cable installations. A Pt100 remains the norm for reference-grade four-wire work, where lead resistance is cancelled anyway and lower self-heating power matters.
Why does my sensor read 100.2 Ω in an ice bath?: An ice point should read 100.00 Ω. 100.2 Ω is +0.51 °C, which is outside Class A (±0.15 °C at 0 °C) and Class B (±0.30 °C). Check the ice bath itself first — a poorly packed bath sits above 0 °C — then lead resistance if the sensor is wired two-wire, then suspect drift or strain in the element.

Values are computed in this page from the IEC 60751:2008 equation and coefficients, by the same tested code the calculator uses. IEC 60751 itself is published by the International Electrotechnical Commission and should be consulted for the definitive text; ValiTrac does not distribute it.