What are the octave band center frequencies?

The nominal octave-band centres are 16, 31.5, 63, 125, 250, 500, 1000, 2000, 4000, 8000 and 16000 Hz. The 1/3-octave series adds two bands between each: 12.5, 16, 20, 25, 31.5, 40, 50, 63, 80, 100, 125, 160, 200, 250, 315, 400, 500, 630, 800, 1000, 1250, 1600, 2000, 2500, 3150, 4000, 5000, 6300, 8000, 10000, 12500, 16000 and 20000 Hz.

How do you calculate octave band edges?

With the IEC 61260-1 base-10 ratio G = 10^0.3, the lower edge is fm × G^(−1/2) = fm × 10^(−0.15) ≈ 0.7079 fm and the upper edge is fm × 10^0.15 ≈ 1.4125 fm. For 1/3-octave bands the factors are 10^(±0.05), about 0.8913 and 1.1220. With base 2 they are 2^(±1/2) and 2^(±1/6).

What standard does this follow, base-10 or base-2?

IEC 61260-1:2014, adopted in the US as ANSI/ASA S1.11-2014 Part 1, specifies the base-10 ratio G = 10^(3/10). The earlier IEC 61260:1995 and ANSI S1.11-2004 also permitted base 2 (G = 2). The two series agree at 1 kHz and drift apart slightly away from it: the 31.5 Hz octave centre is 31.62 Hz in base 10 and 31.25 Hz in base 2.

Why do nominal centre frequencies differ from the exact values?

Nominal values such as 31.5, 63 and 125 Hz are the exact centres rounded to preferred numbers so they are easy to label. Use the exact centre and edges when you design or check filters, and the nominal label when you report data.

How do I add octave band levels to get dB(A)?

Add the A-weighting correction to each band level, convert each to energy, sum and convert back: L_A = 10·log₁₀ Σ 10^((Lᵢ + Aᵢ)/10). For example 80 dB in the 125 Hz band (A = −16.1) and 80 dB at 1 kHz (A = 0) give 10·log₁₀(10^6.39 + 10^8) ≈ 80.1 dB(A). Type your levels into the table to do this automatically.

How do 1/3-octave levels relate to the octave level?

An octave band contains three 1/3-octave bands, so the octave level is the energy sum of the three: L = 10·log₁₀(10^(L₁/10) + 10^(L₂/10) + 10^(L₃/10)). Three equal thirds give an octave level 4.77 dB higher; conversely, a flat octave level split evenly is 4.77 dB lower in each third.

How many 1/3-octave bands are there in the audible range?

There are 31 standard 1/3-octave bands from 20 Hz to 20 kHz (band numbers 13 to 43), or 34 if the 10, 12.5 and 16 Hz bands are included as in the table here.

What is the bandwidth of each octave band?

An octave band spans a 2:1 ratio (exactly 10^0.3 ≈ 1.995 in base 10), so its bandwidth is about 70.5% of the centre frequency, for example 707.9 to 1412.5 Hz at 1 kHz. A 1/3-octave band spans about 23.1% of its centre.

Octave Band Calculator

Octave-band centres are 1000 × 10^(3x/10) Hz and edges sit a factor 10^0.15 (≈ √2) either side; for 1/3-octave bands the step is 10^0.1 and the edge factor 10^0.05. The table lists every band from 10 Hz to 20 kHz with A- and C-weighting, and adds up your band levels into dB, dB(A) and dB(C).

The standard octave-band centre frequencies are 31.5, 63, 125, 250, 500, 1000, 2000, 4000, 8000 and 16000 Hz, and the 1/3-octave bands add two between each (for example 800, 1000, 1250 Hz).

Band Settings

Band Type

Frequency ratio

Find the band for a frequency (Hz)

Selects the band whose edges contain your frequency.

Overall level

Type band levels (dB) in the Level column. Empty bands are skipped.

dB (Z)

—

dB(A)

—

dB(C)

—

L = 10·log₁₀ Σ 10^((Lᵢ + Wᵢ)/10)

Standard Frequency Bands

1/3 Octave · base 10

Nominal (Hz)	Center (Hz)	Lower (Hz)	Upper (Hz)	BW (Hz)	A (dB)	C (dB)
10	10.00	8.91	11.22	2.31	-70.4	-14.3
12.5	12.59	11.22	14.13	2.91	-63.4	-11.3
16	15.85	14.13	17.78	3.66	-56.7	-8.5
20	19.95	17.78	22.39	4.60	-50.5	-6.2
25	25.12	22.39	28.18	5.80	-44.7	-4.4
31.5	31.62	28.18	35.48	7.30	-39.4	-3.0
40	39.81	35.48	44.67	9.19	-34.6	-2.0
50	50.12	44.67	56.23	11.57	-30.2	-1.3
63	63.10	56.23	70.79	14.56	-26.2	-0.8
80	79.43	70.79	89.13	18.33	-22.5	-0.5
100	100.0	89.13	112.2	23.08	-19.1	-0.3
125	125.9	112.2	141.3	29.05	-16.1	-0.2
160	158.5	141.3	177.8	36.57	-13.4	-0.1
200	199.5	177.8	223.9	46.04	-10.9	0.0
250	251.2	223.9	281.8	57.97	-8.6	0.0
315	316.2	281.8	354.8	72.98	-6.6	0.0
400	398.1	354.8	446.7	91.87	-4.8	0.0
500	501.2	446.7	562.3	115.7	-3.2	0.0
630	631.0	562.3	707.9	145.6	-1.9	0.0
800	794.3	707.9	891.3	183.3	-0.8	0.0
1k	1000	891.3	1122	230.8	0.0	0.0
1.25k	1259	1122	1413	290.5	+0.6	0.0
1.6k	1585	1413	1778	365.7	+1.0	-0.1
2k	1995	1778	2239	460.4	+1.2	-0.2
2.5k	2512	2239	2818	579.7	+1.3	-0.3
3.15k	3162	2818	3548	729.8	+1.2	-0.5
4k	3981	3548	4467	918.7	+1.0	-0.8
5k	5012	4467	5623	1157	+0.5	-1.3
6.3k	6310	5623	7079	1456	-0.1	-2.0
8k	7943	7079	8913	1833	-1.1	-3.0
10k	10000	8913	11220	2308	-2.5	-4.4
12.5k	12589	11220	14125	2905	-4.3	-6.2
16k	15849	14125	17783	3657	-6.6	-8.5
20k	19953	17783	22387	4604	-9.3	-11.3

Click a row for band details. Exact values per IEC 61260-1 (fm = 1000 × G^(x/b)); weightings per IEC 61672-1 at the exact centre.

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Quick answer

The standard octave-band centre frequencies are 31.5, 63, 125, 250, 500, 1000, 2000, 4000, 8000 and 16000 Hz, and the 1/3-octave bands add two between each (for example 800, 1000, 1250 Hz). IEC 61260-1 defines the exact centres as fm = 1000 × G^(x/b) with G = 10^(3/10), b = 1 for octaves and 3 for thirds; the band edges are fm × G^(±1/(2b)). Nominal labels are those values rounded to the R10 preferred numbers.

Examples

Band (nominal)	Exact centre	Lower edge	Upper edge	A-weighting
125 Hz octave	125.89 Hz	89.13 Hz	177.8 Hz	−16.1 dB
1 kHz octave	1000 Hz	707.9 Hz	1413 Hz	0.0 dB
1 kHz 1/3-octave	1000 Hz	891.3 Hz	1122 Hz	0.0 dB
63 Hz 1/3-octave	63.10 Hz	56.23 Hz	70.79 Hz	−26.2 dB

Switch between octave and 1/3-octave, base-10 and base-2, or type band levels into the table to get the overall dB(A).

Summary

This calculator lists every octave and 1/3-octave band from 10 Hz to 20 kHz with its nominal label, exact centre frequency, lower and upper edge, bandwidth and A- and C-weighting. Exact values follow IEC 61260-1:2014, which uses the base-10 ratio G = 10^0.3 ≈ 1.9953 and a 1000 Hz reference; a base-2 option (G = 2) reproduces the alternative series allowed by older editions and by some analyzers. Type a frequency to see which band contains it, or enter measured band levels in the table to add them on an energy basis into the overall unweighted, A-weighted and C-weighted level.

How it works

Choose octave (1/1) or 1/3-octave bands and the base-10 (IEC 61260-1) or base-2 ratio.
Each band's exact centre is fm = 1000 × G^(x/b), where x is the band number (0 at 1 kHz) and b = 1 or 3. The edges are fm × G^(−1/(2b)) and fm × G^(+1/(2b)), so the bandwidth is 70.5% of fm for octaves and 23.1% for thirds.
A- and C-weighting come from the IEC 61672-1 analytic formulas evaluated at the exact centre frequency, rounded to 0.1 dB.
Type any frequency to find the band whose edges contain it, or click a row for the band details and a copy button.
Enter measured levels in the Level column: the totals add them as L = 10·log₁₀ Σ 10^(Lᵢ/10), with and without the A and C weighting.

Use cases

Set filter centre frequencies and edges on a real-time analyzer (RTA) or sound level meter.
Convert an octave-band noise spectrum into an overall dB(A) or dB(C) level.
Check which 1/3-octave band a tone, hum or resonance falls into.
Prepare octave-band data for room acoustics, HVAC noise or NR/NC rating work.
Verify filter specifications in datasheets against IEC 61260-1 band edges.
Teach the difference between nominal and exact band frequencies.

Frequently Asked Questions

Last updated: 2026-10-10 · Reviewed by Nham Vu