WormFood's AVR Baud Rate Calculator


Bit Rate Consider only 8-bit UBRR values as being valid (useful for older AVRs)
Clock Freq, in MHz Hide additional U2X=1 double speed mode information (useful for older AVRs)
Data bits+parity Hide actual bit rate on tables.
No color (B/W only)
Show table of all possible bit rates (and their UBRR values), for a given clock speed
WARNING: Will create insanely large tables, if not limited to 8-bit UBRR values
Show table of all possible clock speeds (and corresponding UBRR values), for a given bit rate
WARNING: Will create insanely large tables, if not limited to 8-bit UBRR values
show additional synchronous mode information
NOTE: This check box does nothing, if one of the two options above are not selected.

fosc = 1.0000 MHz
Bit Rate
(bps)
U2Xn = 0U2Xn = 1
UBRR
(dec)
UBRR
(hex)
Actual
Bit Rate
ErrorUBRR
(dec)
UBRR
(hex)
Actual
Bit Rate
Error
300.002070xCF300.480.2%4160x1A0299.76-0.1%
600.001030x67600.960.2%2070xCF600.960.2%
1200.00510x331201.920.2%1030x671201.920.2%
2400.00250x192403.850.2%510x332403.850.2%
4800.00120x0C4807.690.2%250x194807.690.2%
9600.0060x068928.57-7.0%120x0C9615.380.2%
14.4K30x0315.625K8.5%80x0813.889K-3.5%
19.2K20x0220.833K8.5%60x0617.857K-7.0%
28.8K10x0131.25K8.5%30x0331.25K8.5%
38.4K10x0131.25K-18.6%20x0241.667K8.5%
57.6K00x0062.5K8.5%10x0162.5K8.5%
76.8K00x0062.5K-18.6%10x0162.5K-18.6%
115.2K00x0062.5K-45.7%00x00125K8.5%
230.4K00x0062.5K-72.9%00x00125K-45.7%
250K00x0062.5K-75.0%00x00125K-50.0%
0.5M00x0062.5K-87.5%00x00125K-75.0%
1M00x0062.5K-93.8%00x00125K-87.5%
Max.62.5 Kbps125 Kbps
fosc = 1.8432 MHz
Bit Rate
(bps)
U2Xn = 0U2Xn = 1
UBRR
(dec)
UBRR
(hex)
Actual
Bit Rate
ErrorUBRR
(dec)
UBRR
(hex)
Actual
Bit Rate
Error
300.003830x17F300.000.0%7670x2FF300.000.0%
600.001910xBF600.000.0%3830x17F600.000.0%
1200.00950x5F1200.000.0%1910xBF1200.000.0%
2400.00470x2F2400.000.0%950x5F2400.000.0%
4800.00230x174800.000.0%470x2F4800.000.0%
9600.00110x0B9600.000.0%230x179600.000.0%
14.4K70x0714.4K0.0%150x0F14.4K0.0%
19.2K50x0519.2K0.0%110x0B19.2K0.0%
28.8K30x0328.8K0.0%70x0728.8K0.0%
38.4K20x0238.4K0.0%50x0538.4K0.0%
57.6K10x0157.6K0.0%30x0357.6K0.0%
76.8K10x0157.6K-25.0%20x0276.8K0.0%
115.2K00x00115.2K0.0%10x01115.2K0.0%
230.4K00x00115.2K-50.0%00x00230.4K0.0%
250K00x00115.2K-53.9%00x00230.4K-7.8%
0.5M00x00115.2K-77.0%00x00230.4K-53.9%
1M00x00115.2K-88.5%00x00230.4K-77.0%
Max.115.2 Kbps230.4 Kbps
fosc = 2.0000 MHz
Bit Rate
(bps)
U2Xn = 0U2Xn = 1
UBRR
(dec)
UBRR
(hex)
Actual
Bit Rate
ErrorUBRR
(dec)
UBRR
(hex)
Actual
Bit Rate
Error
300.004160x1A0299.76-0.1%8320x340300.120.0%
600.002070xCF600.960.2%4160x1A0599.52-0.1%
1200.001030x671201.920.2%2070xCF1201.920.2%
2400.00510x332403.850.2%1030x672403.850.2%
4800.00250x194807.690.2%510x334807.690.2%
9600.00120x0C9615.380.2%250x199615.380.2%
14.4K80x0813.889K-3.5%160x1014.706K2.1%
19.2K60x0617.857K-7.0%120x0C19.23K0.2%
28.8K30x0331.25K8.5%80x0827.778K-3.5%
38.4K20x0241.667K8.5%60x0635.714K-7.0%
57.6K10x0162.5K8.5%30x0362.5K8.5%
76.8K10x0162.5K-18.6%20x0283.333K8.5%
115.2K00x00125K8.5%10x01125K8.5%
230.4K00x00125K-45.7%00x00250K8.5%
250K00x00125K-50.0%00x00250K0.0%
0.5M00x00125K-75.0%00x00250K-50.0%
1M00x00125K-87.5%00x00250K-75.0%
Max.125 Kbps250 Kbps
fosc = 3.6864 MHz
Bit Rate
(bps)
U2Xn = 0U2Xn = 1
UBRR
(dec)
UBRR
(hex)
Actual
Bit Rate
ErrorUBRR
(dec)
UBRR
(hex)
Actual
Bit Rate
Error
300.007670x2FF300.000.0%15350x5FF300.000.0%
600.003830x17F600.000.0%7670x2FF600.000.0%
1200.001910xBF1200.000.0%3830x17F1200.000.0%
2400.00950x5F2400.000.0%1910xBF2400.000.0%
4800.00470x2F4800.000.0%950x5F4800.000.0%
9600.00230x179600.000.0%470x2F9600.000.0%
14.4K150x0F14.4K0.0%310x1F14.4K0.0%
19.2K110x0B19.2K0.0%230x1719.2K0.0%
28.8K70x0728.8K0.0%150x0F28.8K0.0%
38.4K50x0538.4K0.0%110x0B38.4K0.0%
57.6K30x0357.6K0.0%70x0757.6K0.0%
76.8K20x0276.8K0.0%50x0576.8K0.0%
115.2K10x01115.2K0.0%30x03115.2K0.0%
230.4K00x00230.4K0.0%10x01230.4K0.0%
250K00x00230.4K-7.8%10x01230.4K-7.8%
0.5M00x00230.4K-53.9%00x00460.8K-7.8%
1M00x00230.4K-77.0%00x00460.8K-53.9%
Max.230.4 Kbps460.8 Kbps
fosc = 4.0000 MHz
Bit Rate
(bps)
U2Xn = 0U2Xn = 1
UBRR
(dec)
UBRR
(hex)
Actual
Bit Rate
ErrorUBRR
(dec)
UBRR
(hex)
Actual
Bit Rate
Error
300.008320x340300.120.0%16660x682299.94-0.0%
600.004160x1A0599.52-0.1%8320x340600.240.0%
1200.002070xCF1201.920.2%4160x1A01199.04-0.1%
2400.001030x672403.850.2%2070xCF2403.850.2%
4800.00510x334807.690.2%1030x674807.690.2%
9600.00250x199615.380.2%510x339615.380.2%
14.4K160x1014.706K2.1%340x2214.286K-0.8%
19.2K120x0C19.23K0.2%250x1919.23K0.2%
28.8K80x0827.778K-3.5%160x1029.412K2.1%
38.4K60x0635.714K-7.0%120x0C38.462K0.2%
57.6K30x0362.5K8.5%80x0855.556K-3.5%
76.8K20x0283.333K8.5%60x0671.429K-7.0%
115.2K10x01125K8.5%30x03125K8.5%
230.4K00x00250K8.5%10x01250K8.5%
250K00x00250K0.0%10x01250K0.0%
0.5M00x00250K-50.0%00x000.5M0.0%
1M00x00250K-75.0%00x000.5M-50.0%
Max.250 Kbps0.5 Mbps
fosc = 7.3728 MHz
Bit Rate
(bps)
U2Xn = 0U2Xn = 1
UBRR
(dec)
UBRR
(hex)
Actual
Bit Rate
ErrorUBRR
(dec)
UBRR
(hex)
Actual
Bit Rate
Error
300.0015350x5FF300.000.0%30710xBFF300.000.0%
600.007670x2FF600.000.0%15350x5FF600.000.0%
1200.003830x17F1200.000.0%7670x2FF1200.000.0%
2400.001910xBF2400.000.0%3830x17F2400.000.0%
4800.00950x5F4800.000.0%1910xBF4800.000.0%
9600.00470x2F9600.000.0%950x5F9600.000.0%
14.4K310x1F14.4K0.0%630x3F14.4K0.0%
19.2K230x1719.2K0.0%470x2F19.2K0.0%
28.8K150x0F28.8K0.0%310x1F28.8K0.0%
38.4K110x0B38.4K0.0%230x1738.4K0.0%
57.6K70x0757.6K0.0%150x0F57.6K0.0%
76.8K50x0576.8K0.0%110x0B76.8K0.0%
115.2K30x03115.2K0.0%70x07115.2K0.0%
230.4K10x01230.4K0.0%30x03230.4K0.0%
250K10x01230.4K-7.8%30x03230.4K-7.8%
0.5M00x00460.8K-7.8%10x01460.8K-7.8%
1M00x00460.8K-53.9%00x000.922M-7.8%
Max.460.8 Kbps0.922 Mbps
fosc = 8.0000 MHz
Bit Rate
(bps)
U2Xn = 0U2Xn = 1
UBRR
(dec)
UBRR
(hex)
Actual
Bit Rate
ErrorUBRR
(dec)
UBRR
(hex)
Actual
Bit Rate
Error
300.0016660x682299.94-0.0%33320xD04300.030.0%
600.008320x340600.240.0%16660x682599.88-0.0%
1200.004160x1A01199.04-0.1%8320x3401200.480.0%
2400.002070xCF2403.850.2%4160x1A02398.08-0.1%
4800.001030x674807.690.2%2070xCF4807.690.2%
9600.00510x339615.380.2%1030x679615.380.2%
14.4K340x2214.286K-0.8%680x4414.493K0.6%
19.2K250x1919.23K0.2%510x3319.23K0.2%
28.8K160x1029.412K2.1%340x2228.571K-0.8%
38.4K120x0C38.462K0.2%250x1938.462K0.2%
57.6K80x0855.556K-3.5%160x1058.824K2.1%
76.8K60x0671.429K-7.0%120x0C76.923K0.2%
115.2K30x03125K8.5%80x08111.111K-3.5%
230.4K10x01250K8.5%30x03250K8.5%
250K10x01250K0.0%30x03250K0.0%
0.5M00x000.5M0.0%10x010.5M0.0%
1M00x000.5M-50.0%00x001M0.0%
Max.0.5 Mbps1 Mbps
fosc = 11.0592 MHz
Bit Rate
(bps)
U2Xn = 0U2Xn = 1
UBRR
(dec)
UBRR
(hex)
Actual
Bit Rate
ErrorUBRR
(dec)
UBRR
(hex)
Actual
Bit Rate
Error
300.0023030x8FF300.000.0%46070x11FF300.000.0%
600.0011510x47F600.000.0%23030x8FF600.000.0%
1200.005750x23F1200.000.0%11510x47F1200.000.0%
2400.002870x11F2400.000.0%5750x23F2400.000.0%
4800.001430x8F4800.000.0%2870x11F4800.000.0%
9600.00710x479600.000.0%1430x8F9600.000.0%
14.4K470x2F14.4K0.0%950x5F14.4K0.0%
19.2K350x2319.2K0.0%710x4719.2K0.0%
28.8K230x1728.8K0.0%470x2F28.8K0.0%
38.4K170x1138.4K0.0%350x2338.4K0.0%
57.6K110x0B57.6K0.0%230x1757.6K0.0%
76.8K80x0876.8K0.0%170x1176.8K0.0%
115.2K50x05115.2K0.0%110x0B115.2K0.0%
230.4K20x02230.4K0.0%50x05230.4K0.0%
250K20x02230.4K-7.8%50x05230.4K-7.8%
0.5M00x000.691M38.2%20x02460.8K-7.8%
1M00x000.691M-30.9%00x001.382M38.2%
Max.0.691 Mbps1.382 Mbps
fosc = 14.7456 MHz
Bit Rate
(bps)
U2Xn = 0U2Xn = 1
UBRR
(dec)
UBRR
(hex)
Actual
Bit Rate
ErrorUBRR
(dec)
UBRR
(hex)
Actual
Bit Rate
Error
300.0030710xBFF300.000.0%61430x17FF300.000.0%
600.0015350x5FF600.000.0%30710xBFF600.000.0%
1200.007670x2FF1200.000.0%15350x5FF1200.000.0%
2400.003830x17F2400.000.0%7670x2FF2400.000.0%
4800.001910xBF4800.000.0%3830x17F4800.000.0%
9600.00950x5F9600.000.0%1910xBF9600.000.0%
14.4K630x3F14.4K0.0%1270x7F14.4K0.0%
19.2K470x2F19.2K0.0%950x5F19.2K0.0%
28.8K310x1F28.8K0.0%630x3F28.8K0.0%
38.4K230x1738.4K0.0%470x2F38.4K0.0%
57.6K150x0F57.6K0.0%310x1F57.6K0.0%
76.8K110x0B76.8K0.0%230x1776.8K0.0%
115.2K70x07115.2K0.0%150x0F115.2K0.0%
230.4K30x03230.4K0.0%70x07230.4K0.0%
250K30x03230.4K-7.8%60x06263.314K5.3%
0.5M10x01460.8K-7.8%30x03460.8K-7.8%
1M00x000.922M-7.8%10x010.922M-7.8%
Max.0.922 Mbps1.843 Mbps
fosc = 16.0000 MHz
Bit Rate
(bps)
U2Xn = 0U2Xn = 1
UBRR
(dec)
UBRR
(hex)
Actual
Bit Rate
ErrorUBRR
(dec)
UBRR
(hex)
Actual
Bit Rate
Error
300.0033320xD04300.030.0%66660x1A0A299.99-0.0%
600.0016660x682599.88-0.0%33320xD04600.060.0%
1200.008320x3401200.480.0%16660x6821199.76-0.0%
2400.004160x1A02398.08-0.1%8320x3402400.960.0%
4800.002070xCF4807.690.2%4160x1A04796.16-0.1%
9600.001030x679615.380.2%2070xCF9615.380.2%
14.4K680x4414.493K0.6%1380x8A14.388K-0.1%
19.2K510x3319.23K0.2%1030x6719.23K0.2%
28.8K340x2228.571K-0.8%680x4428.986K0.6%
38.4K250x1938.462K0.2%510x3338.462K0.2%
57.6K160x1058.824K2.1%340x2257.143K-0.8%
76.8K120x0C76.923K0.2%250x1976.923K0.2%
115.2K80x08111.111K-3.5%160x10117.647K2.1%
230.4K30x03250K8.5%80x08222.222K-3.5%
250K30x03250K0.0%70x07250K0.0%
0.5M10x010.5M0.0%30x030.5M0.0%
1M00x001M0.0%10x011M0.0%
Max.1 Mbps2 Mbps
fosc = 18.4320 MHz
Bit Rate
(bps)
U2Xn = 0U2Xn = 1
UBRR
(dec)
UBRR
(hex)
Actual
Bit Rate
ErrorUBRR
(dec)
UBRR
(hex)
Actual
Bit Rate
Error
300.0038390xEFF300.000.0%76790x1DFF300.000.0%
600.0019190x77F600.000.0%38390xEFF600.000.0%
1200.009590x3BF1200.000.0%19190x77F1200.000.0%
2400.004790x1DF2400.000.0%9590x3BF2400.000.0%
4800.002390xEF4800.000.0%4790x1DF4800.000.0%
9600.001190x779600.000.0%2390xEF9600.000.0%
14.4K790x4F14.4K0.0%1590x9F14.4K0.0%
19.2K590x3B19.2K0.0%1190x7719.2K0.0%
28.8K390x2728.8K0.0%790x4F28.8K0.0%
38.4K290x1D38.4K0.0%590x3B38.4K0.0%
57.6K190x1357.6K0.0%390x2757.6K0.0%
76.8K140x0E76.8K0.0%290x1D76.8K0.0%
115.2K90x09115.2K0.0%190x13115.2K0.0%
230.4K40x04230.4K0.0%90x09230.4K0.0%
250K40x04230.4K-7.8%80x08256K2.4%
0.5M10x010.576M15.2%40x04460.8K-7.8%
1M00x001.152M15.2%10x011.152M15.2%
Max.1.152 Mbps2.304 Mbps
fosc = 20.0000 MHz
Bit Rate
(bps)
U2Xn = 0U2Xn = 1
UBRR
(dec)
UBRR
(hex)
Actual
Bit Rate
ErrorUBRR
(dec)
UBRR
(hex)
Actual
Bit Rate
Error
300.0041660x1046299.98-0.0%83320x208C300.010.0%
600.0020820x822600.100.0%41660x1046599.95-0.0%
1200.0010410x4111199.62-0.0%20820x8221200.190.0%
2400.005200x2082399.23-0.0%10410x4112399.23-0.0%
4800.002590x1034807.690.2%5200x2084798.46-0.0%
9600.001290x819615.380.2%2590x1039615.380.2%
14.4K860x5614.368K-0.2%1730xAD14.368K-0.2%
19.2K640x4019.23K0.2%1290x8119.23K0.2%
28.8K420x2A29.070K0.9%860x5628.736K-0.2%
38.4K320x2037.879K-1.4%640x4038.462K0.2%
57.6K210x1556.818K-1.4%420x2A58.140K0.9%
76.8K150x0F78.125K1.7%320x2075.758K-1.4%
115.2K100x0A113.636K-1.4%210x15113.636K-1.4%
230.4K40x04250K8.5%100x0A227.273K-1.4%
250K40x04250K0.0%90x09250K0.0%
0.5M20x02416.667K-16.7%40x040.5M0.0%
1M00x001.25M25.0%20x020.833M-16.7%
Max.1.25 Mbps2.5 Mbps
Please note, that the colors will change, depending on your data bits+parity selection.
Please see the Atmel manual for your AVR for more details about how the data bits+parity, and U2X=1 settings affect the maximum allowable error rate.
Legend:
UBRR and clock speed are 0.5% or less off
UBRR and clock speed are within the recommended maximum error rate (1% to 3%)
UBRR and clock speed is in the lower half, between recommended and absolute max error rates
UBRR and clock speed is in the upper half, between recommended and absolute max error rates
UBRR and clock speed are outside of the absolute maximum error rate. (3.23% to 6.67%)
UBRR out of range, or more than twice the absolute maximum error rate (6.46% to 13.34%)
Recommended Maximum Receiver Bit Rate Error for Normal Speed Mode (U2X=0)
D
# (Data+Parity Bit)
Rslow(%)Rfast(%)Max. total error (%)Recommended max.
receiver error (%)
593.20106.67+6.67/-6.8±3.0
694.12105.79+5.79/-5.88±2.5
794.81105.11+5.11/-5.19±2.0
895.36104.58+4.58/-4.54±2.0
995.81104.14+4.14/-4.19±1.5
1096.17103.78+3.78/-3.83±1.5
Recommended Maximum Receiver Bit Rate Error for Double Speed Mode (U2X=1)
D
# (Data+Parity Bit)
Rslow(%)Rfast(%)Max. total error (%)Recommended max.
receiver error (%)
594.12105.66+5.66/-5.88±2.5
694.92104.92+4.92/-5.08±2.0
795.52104.35+4.35/-4.48±1.5
896.00103.90+3.90/-4.00±1.5
996.39103.53+3.53/-3.61±1.5
1096.70103.23+3.23/-3.30±1.0

I call this a "baud rate calculator", however, "baud rate" is technically an incorrect term. It should be called a "bit rate calculator". Because people misuse the term "baud" so frequently, many do not know there is a difference between "bit rate" and "baud rate". Since Atmel uses the term "baud rate" in their AVR manuals and data sheets, it seems natural to name this a "baud rate calculator", even though I know it's abuse of the word "baud". I use the term "baud rate" on this page, knowing it is wrong, so people would be able to find this page, when searching the web, (even Atmel uses "baud rate") however, all other references are as "bit rate".

NOTE about the UBRR register(s): Some AVRs only have a single UBRR register, while other AVRs have two UBRR registers. If your AVR has only 1 UBRR register, then you can check the box "Consider only 8-bit UBRR values as being valid" to have it show you when the UBRR value is out of range for your AVR. If your AVR handles a 12-bit UBRR value, then the UBRR value in hexadecimal will be helpful to you, because it will make it easier to find the UBRRH and UBRRL values (I'm sure you can figure out what goes where).

NOTE about XMEGA AVRs: The UBRR values generated, can be used as the BSEL value in the XMEGA AVRs, if and only if you set BSCALE to zero. If there is enough interest for this calculator to support the XMEGA series, then I will add BSCALE calculations to the list, but for now, there is no easy way to to calculate BSCALE without already knowing knowing what BSEL value you want to use, so it's computationally expensive to calculate.

How to use this page:
Without entering anything, you can get a list of the UBRR settings for many popular clock speeds, and serial port bit rates. What makes this program special, is the fact that you can tell it what serial port bit rate you want, and it will tell you all the possible clock speeds that will generate your desired serial port bit rate. You can also give it a clock speed, and it will tell you all the possible serial port bit rates that can be producted with that clock speed. This is very handy when you are searching through your "junk pile", looking for the right crystal, or oscillator to generate a given serial port bit rate.
If you enter a serial port bit rate, not already listed, then the serial port bit rate will be listed as the last entry on each clock speed table. If you enter a clock speed that is not already listed, then a new clock speed table will be generated as the first table, with your clock speed.


If you notice any errors, please, please, please report them to me. If you would like to contact me about this program, if you have any questions or requests then stop by channel #avr on the FreeNode IRC network.

AVRBaudCalc is ©2005-2016 by WormFood