This instrument is the National Measurement (Recognized-Value Standard of Measurement of the Density of Water) Determination 2026.

(1) Each provision of this instrument specified in column 1 of the table commences, or is taken to have commenced, in accordance with column 2 of the table. Any other statement in column 2 has effect according to its terms.

Commencement information
Column 1	Column 2	Column 3
Provisions	Commencement	Date/Details
The whole of this instrument	The day after this instrument is registered.

Note: This table relates only to the provisions of this instrument as originally made. It will not be amended to deal with any later amendments of this instrument.

(2) Any information in column 3 of the table is not part of this instrument. Information may be inserted in this column, or information in it may be edited, in any published version of this instrument.

3 Authority

This instrument is made under paragraphs 8A(1)(a) and (b) of the National Measurement Act 1960.

4 Schedules

Each instrument that is specified in a Schedule to this instrument is amended or repealed as set out in the applicable items in the Schedule concerned, and any other item in a Schedule to this instrument has effect according to its terms.

5 Definitions

Note: Recognized-value standard of measurement is defined in the Act.

In this instrument:

Act means the National Measurement Act 1960.

6 Recognized-Value Standard of Measurement of the Density of Water

The magnitude of the density of water dt at a temperature t and a mean pressure p, provided t lies within the range 0 °C to 40 °C and p lies within the range 2 × 104 Pa to 106 Pa, is a Recognized-Value Standard of Measurement determined as follows:
1. When p is 101325 Pa and t is one of the temperatures listed in Schedule 1 the magnitude of the density in kg·m-3 is as stated in Schedule 1, which is derived from the following formula:

$Start formula d subscript t equals 999.972 minus start fraction open bracket t minus 3.98419 close bracket superscript 2 over 506.60312 end fraction times start fraction open bracket t plus 286.4601 close bracket over open bracket t plus 67.7601 close bracket end fraction end formula$

where:

dt is the density in kg m−3

t is the temperature in ℃.

When p is 101325 Pa and t is between two adjacent values of temperature listed in Schedule 1 then the magnitude of the density in kg·m-3 shall be determined from Schedule 1 by linear interpolation.
When p differs from 101325 Pa the magnitude of the density in kg·m-3 as stated in Schedule 1 or derived in accordance with the above linear interpolation shall be algebraically increased by an amount equal to:

If the value of t used in Schedule 1 and the above equations does not differ from the true mean temperature of the water by more than 0.1 °C, if the value of p used in the equation does not differ from the true mean pressure within the water by more than 1000 Pa, and if impurities in the water do not exceed 1 part in 105 by mass, the chance is not more than one in one hundred that the density so ascertained differs from the true value of density by more than 0.05 kg·m-3.

Schedule 1— The Density of Water in Kilograms per Cubic Metre as a Function of Temperature in Degrees Celsius

Temperature (°C)	Density (kg.m-3)	Temperature (°C)	Density (kg.m-3)	Temperature (°C)	Density (kg.m-3)	Temperature (°C)	Density (kg.m-3)
0.0	999.839	10.0	999.700	20.0	998.204	30.0	995.647
0.1	999.846	10.1	999.691	20.1	998.183	30.1	995.617
0.2	999.853	10.2	999.682	20.2	998.163	30.2	995.587
0.3	999.859	10.3	999.673	20.3	998.142	30.3	995.556
0.4	999.865	10.4	999.663	20.4	998.121	30.4	995.526
0.5	999.871	10.5	999.654	20.5	998.100	30.5	995.495
0.6	999.877	10.6	999.645	20.6	998.078	30.6	995.465
0.7	999.883	10.7	999.635	20.7	998.057	30.7	995.434
0.8	999.888	10.8	999.625	20.8	998.036	30.8	995.403
0.9	999.893	10.9	999.615	20.9	998.014	30.9	995.372
1.0	999.898	11.0	999.605	21.0	997.992	31.0	995.341
1.1	999.903	11.1	999.595	21.1	997.971	31.1	995.310
1.2	999.908	11.2	999.585	21.2	997.949	31.2	995.279
1.3	999.913	11.3	999.574	21.3	997.927	31.3	995.248
1.4	999.917	11.4	999.564	21.4	997.905	31.4	995.216
1.5	999.921	11.5	999.553	21.5	997.883	31.5	995.185
1.6	999.925	11.6	999.542	21.6	997.860	31.6	995.153
1.7	999.929	11.7	999.531	21.7	997.838	31.7	995.122
1.8	999.933	11.8	999.520	21.8	997.816	31.8	995.090
1.9	999.936	11.9	999.509	21.9	997.793	31.9	995.058
2.0	999.940	12.0	999.497	22.0	997.770	32.0	995.026
2.1	999.943	12.1	999.486	22.1	997.748	32.1	994.995
2.2	999.946	12.2	999.474	22.2	997.725	32.2	994.962
2.3	999.949	12.3	999.463	22.3	997.702	32.3	994.930
2.4	999.952	12.4	999.451	22.4	997.679	32.4	994.898
2.5	999.954	12.5	999.439	22.5	997.656	32.5	994.866
2.6	999.956	12.6	999.427	22.6	997.632	32.6	994.834
2.7	999.959	12.7	999.415	22.7	997.609	32.7	994.801
2.8	999.961	12.8	999.402	22.8	997.586	32.8	994.769
2.9	999.962	12.9	999.390	22.9	997.562	32.9	994.736
3.0	999.964	13.0	999.377	23.0	997.538	33.0	994.703
3.1	999.966	13.1	999.364	23.1	997.515	33.1	994.670
3.2	999.967	13.2	999.352	23.2	997.491	33.2	994.638
3.3	999.968	13.3	999.339	23.3	997.467	33.3	994.605
3.4	999.969	13.4	999.326	23.4	997.443	33.4	994.572
3.5	999.970	13.5	999.312	23.5	997.419	33.5	994.539
3.6	999.971	13.6	999.299	23.6	997.394	33.6	994.505
3.7	999.971	13.7	999.286	23.7	997.370	33.7	994.472
3.8	999.972	13.8	999.272	23.8	997.346	33.8	994.439
3.9	999.972	13.9	999.258	23.9	997.321	33.9	994.405
4.0	999.972	14.0	999.244	24.0	997.297	34.0	994.372
4.1	999.972	14.1	999.230	24.1	997.272	34.1	994.338
4.2	999.972	14.2	999.216	24.2	997.247	34.2	994.304
4.3	999.971	14.3	999.202	24.3	997.222	34.3	994.271
4.4	999.971	14.4	999.188	24.4	997.197	34.4	994.237
4.5	999.970	14.5	999.173	24.5	997.172	34.5	994.203
4.6	999.969	14.6	999.159	24.6	997.147	34.6	994.169
4.7	999.968	14.7	999.144	24.7	997.121	34.7	994.135
4.8	999.967	14.8	999.130	24.8	997.096	34.8	994.101
4.9	999.965	14.9	999.115	24.9	997.071	34.9	994.066
5.0	999.964	15.0	999.100	25.0	997.045	35.0	994.032
5.1	999.962	15.1	999.084	25.1	997.019	35.1	993.998
5.2	999.960	15.2	999.069	25.2	996.993	35.2	993.963
5.3	999.958	15.3	999.054	25.3	996.968	35.3	993.929
5.4	999.956	15.4	999.038	25.4	996.942	35.4	993.894
5.5	999.954	15.5	999.023	25.5	996.916	35.5	993.859
5.6	999.952	15.6	999.007	25.6	996.889	35.6	993.824
5.7	999.949	15.7	998.991	25.7	996.863	35.7	993.790
5.8	999.946	15.8	998.975	25.8	996.837	35.8	993.755
5.9	999.943	15.9	998.959	25.9	996.810	35.9	993.719
6.0	999.940	16.0	998.943	26.0	996.784	36.0	993.684
6.1	999.937	16.1	998.927	26.1	996.757	36.1	993.649
6.2	999.934	16.2	998.910	26.2	996.730	36.2	993.614
6.3	999.930	16.3	998.894	26.3	996.704	36.3	993.578
6.4	999.927	16.4	998.877	26.4	996.677	36.4	993.543
6.5	999.923	16.5	998.860	26.5	996.650	36.5	993.508
6.6	999.919	16.6	998.843	26.6	996.623	36.6	993.472
6.7	999.915	16.7	998.827	26.7	996.595	36.7	993.436
6.8	999.910	16.8	998.809	26.8	996.568	36.8	993.400
6.9	999.906	16.9	998.792	26.9	996.541	36.9	993.365
7.0	999.902	17.0	998.775	27.0	996.513	37.0	993.329
7.1	999.897	17.1	998.757	27.1	996.486	37.1	993.293
7.2	999.892	17.2	998.740	27.2	996.458	37.2	993.257
7.3	999.887	17.3	998.722	27.3	996.430	37.3	993.221
7.4	999.882	17.4	998.704	27.4	996.403	37.4	993.184
7.5	999.877	17.5	998.687	27.5	996.375	37.5	993.148
7.6	999.871	17.6	998.669	27.6	996.347	37.6	993.112
7.7	999.866	17.7	998.650	27.7	996.318	37.7	993.075
7.8	999.860	17.8	998.632	27.8	996.290	37.8	993.039
7.9	999.854	17.9	998.614	27.9	996.262	37.9	993.002
8.0	999.848	18.0	998.596	28.0	996.234	38.0	992.965
8.1	999.842	18.1	998.577	28.1	996.205	38.1	992.929
8.2	999.836	18.2	998.558	28.2	996.177	38.2	992.892
8.3	999.830	18.3	998.540	28.3	996.148	38.3	992.855
8.4	999.823	18.4	998.521	28.4	996.119	38.4	992.818
8.5	999.816	18.5	998.502	28.5	996.090	38.5	992.781
8.6	999.810	18.6	998.483	28.6	996.062	38.6	992.743
8.7	999.803	18.7	998.463	28.7	996.033	38.7	992.706
8.8	999.795	18.8	998.444	28.8	996.003	38.8	992.669
8.9	999.788	18.9	998.425	28.9	995.974	38.9	992.632
9.0	999.781	19.0	998.405	29.0	995.945	39.0	992.594
9.1	999.773	19.1	998.386	29.1	995.916	39.1	992.557
9.2	999.766	19.2	998.366	29.2	995.886	39.2	992.519
9.3	999.758	19.3	998.346	29.3	995.857	39.3	992.481
9.4	999.750	19.4	998.326	29.4	995.827	39.4	992.444
9.5	999.742	19.5	998.306	29.5	995.797	39.5	992.406
9.6	999.734	19.6	998.286	29.6	995.768	39.6	992.368
9.7	999.725	19.7	998.266	29.7	995.738	39.7	992.330
9.8	999.717	19.8	998.245	29.8	995.708	39.8	992.292
9.9	999.708	19.9	998.225	29.9	995.678	39.9	992.254
10.0	999.700	20.0	998.204	30.0	995.647	40.0	992.215

Schedule 2—Repeals

National Measurement Act 1960 - Determination by the National Standards Commission - Recognized-Value Standard of Measurement of Density – Water

1 The whole of the instrument

Repeal the instrument