N.C. Department of Environment and Natural Resources
 Welcome to the North Carolina Division of Air Quality
N.C. Air Awareness Program >> Air Quality Forecast Center >> AQI Calculation Table

Table for Converting 24-Hour PM 2.5 Concentration
in Micrograms per Cubic Meter (µg/m3) to the Air Quality Index (AQI)

Green

ILO = 0
IHI = 50
BPLO = 0.10
BPHI = 15.4

PM2.5 Conc.   AQI
0.0 0.1   0
0.2 0.4   1
0.5 0.7   2
0.8 1.0   3
1.1 1.3   4
1.4 1.6   5
1.7 2.0   6
2.1 2.3   7
2.4 2.6   8
2.7 2.9   9
3.0 3.2   10
3.3 3.5   11
3.6 3.8   12
3.9 4.1   13
4.2 4.4   14
4.5 4.7   15
4.8 5.0   16
5.1 5.3   17
5.4 5.6   18
5.7 6.0   19
6.1 6.3   20
6.4 6.6   21
6.7 6.9   22
7.0 7.2   23
7.3 7.5   24
7.6 7.8   25
7.9 8.1   26
8.2 8.4   27
8.5 8.7   28
8.8 9.0   29
9.1 9.3   30
9.4 9.7   31
9.8 10.0   32
10.1 10.3   33
10.4 10.6   34
10.7 10.9   35
11.0 11.2   36
11.3 11.5   37
11.6 11.8   38
11.9 12.1   39
12.2 12.4   40
12.5 12.7   41
12.8 13.0   42
13.1 13.3   43
13.4 13.7   44
13.8 14.0   45
14.1 14.3   46
14.4 14.6   47
14.7 14.9   48
15.0 15.2   49
15.3 15.4   50
Yellow

ILO = 51
IHI = 100
BPLO = 15.5
BPHI = 35.4

PM2.5 Conc.   AQI
15.5 15.7   51
15.8 16.1   52
16.2 16.5   53
16.6 16.9   54
17.0 17.3   55
17.4 17.7   56
17.8 18.1   57
18.2 18.5   58
18.6 18.9   59
19.0 19.3   60
19.4 19.7   61
19.8 20.1   62
20.2 20.5   63
20.6 20.9   64
21.0 21.3   65
21.4 21.7   66
21.8 22.2   67
22.3 22.6   68
22.7 23.0   69
23.1 23.4   70
23.5 23.8   71
23.9 24.2   72
24.3 24.6   73
24.7 25.0   74
25.1 25.4   75
25.5 25.8   76
25.9 26.2   77
26.3 26.6   78
26.7 27.0   79
27.1 27.4   80
27.5 27.8   81
27.9 28.2   82
28.3 28.6   83
28.7 29.1   84
29.2 29.5   85
29.6 29.9   86
30.0 30.3   87
30.4 30.7   88
30.8 31.1   89
31.2 31.5   90
31.6 31.9   91
32.0 32.3   92
32.4 32.7   93
32.8 33.1   94
33.2 33.5   95
33.6 33.9   96
34.0 34.3   97
34.4 34.7   98
34.8 35.1   93
35.2 35.4   100
Orange

ILO = 101
IHI = 150
BPLO = 35.5
BPHI = 65.4

PM2.5 Conc.   AQI
35.5 35.8   101
35.9 36.4   102
36.5 37.0   103
37.1 37.6   104
37.7 38.2   105
38.3 38.8   106
38.9 39.4   107
39.5 40.0   108
40.1 40.6   109
40.7 41.2   110
41.3 41.9   111
42.0 42.5   112
42.6 43.1   113
43.2 43.7   114
43.8 44.3   115
44.4 44.9   116
45.0 45.5   117
45.6 46.1   118
46.2 46.7   119
46.8 47.3   120
47.4 48.0   121
48.1 48.6   122
48.7 49.2   123
49.3 49.8   124
49.9 50.4   125
50.5 51.0   126
51.1 51.6   127
51.7 52.2   128
52.3 52.8   129
52.9 53.5   130
53.6 54.1   131
54.2 54.7   132
54.8 55.3   133
55.4 55.9   134
56.0 56.5   135
56.6 57.1   136
57.2 57.7   137
57.8 58.3   138
58.4 58.9   139
59.0 59.6   140
59.7 60.2   141
60.3 60.8   142
60.9 61.4   143
61.5 62.0   144
62.1 62.6   145
62.7 63.2   146
63.3 63.8   147
63.9 64.4   148
64.5 65.0   149
65.1 65.4   150
Red

ILO = 151
IHI = 200
BPLO = 65.4
BPHI = 150.4

PM2.5 Conc.   AQI
65.5 66.3   151
66.4 68.0   152
68.1 69.8   153
69.9 71.5   154
71.6 73.2   155
73.3 75.0   156
75.1 76.7   157
76.8 78.4   158
78.5 80.2   159
80.3 81.9   160
82.0 83.6   161
83.7 85.4   162
85.5 87.1   163
87.2 88.8   164
88.9 90.6   165
90.7 92.3   166
92.4 94.0   167
94.1 95.8   168
95.9 97.5   169
97.6 99.2   170
99.3 101.0   171
101.1 102.7   172
102.8 104.4   173
104.5 106.2   174
106.3 107.9   175
108.0 109.6   176
109.7 111.4   177
111.5 113.1   178
113.2 114.8   179
114.9 116.6   180
116.7 118.3   181
118.4 120.0   182
120.1 121.8   183
121.9 123.5   184
123.6 125.2   185
125.3 127.0   186
127.1 128.7   187
128.8 130.4   188
130.5 132.2   189
132.3 133.9   190
134.0 135.6   191
135.7 137.4   192
137.5 139.1   193
139.2 140.8   194
140.9 142.6   195
142.7 144.3   196
144.4 146.0   197
146.1 147.8   198
147.9 149.5   199
149.6 150.4   200
Purple

ILO = 201
IHI = 300
BPLO = 150.5
BPHI = 250.4

PM2.5 Conc.   AQI
150.5 151.0   201
151.1 152.0   202
152.1 153.0   203
153.1 154.0   204
154.1 155.0   205
155.1 156.0   206
156.1 157.0   207
157.1 158.0   208
158.1 159.0   209
159.1 160.0   210
160.1 161.0   211
161.1 162.1   212
162.2 163.1   213
163.2 164.1   214
164.2 165.1   215
165.2 166.1   216
166.2 167.1   217
167.2 168.1   218
168.2 169.1   219
169.2 170.1   220
170.2 171.1   221
171.2 172.1   222
172.2 173.2   223
173.3 174.2   224
174.3 175.2   225
175.3 176.2   226
176.3 177.2   227
177.3 178.2   228
178.3 179.2   229
179.3 180.2   230
180.3 181.2   231
181.3 182.2   232
182.3 183.2   233
183.3 184.3   234
184.4 185.3   235
185.4 186.3   236
186.4 187.3   237
187.4 188.3   238
188.4 189.3   239
189.4 190.3   240
190.4X 191.3   241
191.4 192.3   242
192.4 193.3   243
193.4 194.3   244
194.4 195.4   245
195.5 196.4   246
196.5 197.4   247
197.5 198.4   248
198.5 199.4   249
199.5 200.4   250
 
AQI Conversion Formula
 AQI = [(Index value at higher limit of category minus Index value at lower limit of category) / (Break-point concentration at upper limit of category minus Break-point concentration at lower limit of category)] multiplied by [8-hour ozone concentration minus Break-point concentration at lower limit of category] plus Index value at lower limit of category

AQI = Air Quality Index
ILO = Index value at the lower limit of the AQI category
IHI = Index value at the upper limit of the AQI category
BPLO = Break-point concentration at lower limit of AQI category
BPHI = Break-point concentration at upper limit of AQI category
CO3 = 8-hour ozone concentration


Email us

Last Modified: Fri June 13 10:26:30 2008
 Visit the NCDENR web portal
Top of Page