AVR UART Baud Rate Calculator

UART baudrate calculator

Online UART bitrate calculator for AVR-microcontrollers. 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.

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.

UBRR and clock speed are 0.1% or less off
UBRR and clock speed are 0.5% or less off
UBRR and clock speed are 1.0% or less off
UBRR and clock speed are 2.0% or less off
UBRR and clock speed are 3.0% or less off
UBRR and clock speed are outside of the absolute maximum error rate

Bit Rate:

Clock Freq, MHz:

fCPU = 1 MHz
Bit RateU2Xn = 0U2Xn = 1
UBRR
(dec)
UBRR
(hex)
Actual
Bit Rate
ErrorUBRR
(dec)
UBRR
(hex)
Actual
Bit Rate
Error
3002070x00CF300.480.2%4160x01A0299.76-0.1%
6001030x0067600.960.2%2070x00CF600.960.2%
900680x0044905.80.6%1380x008A899.28-0.1%
1200510x00331201.920.2%1030x00671201.920.2%
1800340x00221785.71-0.8%680x00441811.590.6%
2400250x00192403.850.2%510x00332403.850.2%
3600160x00103676.472.1%340x00223571.43-0.8%
4800120x000C4807.690.2%250x00194807.690.2%
960060x00068928.57-7%120x000C9615.380.2%
14.4 K30x000315.625 K8.5%80x000813.889 K-3.5%
19.2 K20x000220.833 K8.5%60x000617.857 K-7%
28.8 K10x000131.25 K8.5%30x000331.25 K8.5%
33.6 K10x000131.25 K-7%30x000331.25 K-7%
38.4 K10x000131.25 K-18.6%20x000241.667 K8.5%
56 K00x000062.5 K11.6%10x000162.5 K11.6%
57.6 K00x000062.5 K8.5%10x000162.5 K8.5%
76.8 K00x000062.5 K-18.6%10x000162.5 K-18.6%
115.2 K00x000062.5 K-45.7%00x0000125 K8.5%
128 K00x000062.5 K-51.2%00x0000125 K-2.3%
153.6 K00x000062.5 K-59.3%00x0000125 K-18.6%
230.4 K00x000062.5 K-72.9%00x0000125 K-45.7%
fCPU = 1.8432 MHz
Bit RateU2Xn = 0U2Xn = 1
UBRR
(dec)
UBRR
(hex)
Actual
Bit Rate
ErrorUBRR
(dec)
UBRR
(hex)
Actual
Bit Rate
Error
3003830x017F3000%7670x02FF3000%
6001910x00BF6000%3830x017F6000%
9001270x007F9000%2550x00FF9000%
1200950x005F12000%1910x00BF12000%
1800630x003F18000%1270x007F18000%
2400470x002F24000%950x005F24000%
3600310x001F36000%630x003F36000%
4800230x001748000%470x002F48000%
9600110x000B96000%230x001796000%
14.4 K70x000714.4 K0%150x000F14.4 K0%
19.2 K50x000519.2 K0%110x000B19.2 K0%
28.8 K30x000328.8 K0%70x000728.8 K0%
33.6 K20x000238.4 K14.3%60x000632.914 K-2%
38.4 K20x000238.4 K0%50x000538.4 K0%
56 K10x000157.6 K2.9%30x000357.6 K2.9%
57.6 K10x000157.6 K0%30x000357.6 K0%
76.8 K10x000157.6 K-25%20x000276.8 K0%
115.2 K00x0000115.2 K0%10x0001115.2 K0%
128 K00x0000115.2 K-10%10x0001115.2 K-10%
153.6 K00x0000115.2 K-25%10x0001115.2 K-25%
230.4 K00x0000115.2 K-50%00x0000230.4 K0%
fCPU = 2 MHz
Bit RateU2Xn = 0U2Xn = 1
UBRR
(dec)
UBRR
(hex)
Actual
Bit Rate
ErrorUBRR
(dec)
UBRR
(hex)
Actual
Bit Rate
Error
3004160x01A0299.76-0.1%8320x0340300.120%
6002070x00CF600.960.2%4160x01A0599.52-0.1%
9001380x008A899.28-0.1%2770x0115899.28-0.1%
12001030x00671201.920.2%2070x00CF1201.920.2%
1800680x00441811.590.6%1380x008A1798.56-0.1%
2400510x00332403.850.2%1030x00672403.850.2%
3600340x00223571.43-0.8%680x00443623.190.6%
4800250x00194807.690.2%510x00334807.690.2%
9600120x000C9615.380.2%250x00199615.380.2%
14.4 K80x000813.889 K-3.5%160x001014.706 K2.1%
19.2 K60x000617.857 K-7%120x000C19.231 K0.2%
28.8 K30x000331.25 K8.5%80x000827.778 K-3.5%
33.6 K30x000331.25 K-7%60x000635.714 K6.3%
38.4 K20x000241.667 K8.5%60x000635.714 K-7%
56 K10x000162.5 K11.6%30x000362.5 K11.6%
57.6 K10x000162.5 K8.5%30x000362.5 K8.5%
76.8 K10x000162.5 K-18.6%20x000283.333 K8.5%
115.2 K00x0000125 K8.5%10x0001125 K8.5%
128 K00x0000125 K-2.3%10x0001125 K-2.3%
153.6 K00x0000125 K-18.6%10x0001125 K-18.6%
230.4 K00x0000125 K-45.7%00x0000250 K8.5%
fCPU = 3.6864 MHz
Bit RateU2Xn = 0U2Xn = 1
UBRR
(dec)
UBRR
(hex)
Actual
Bit Rate
ErrorUBRR
(dec)
UBRR
(hex)
Actual
Bit Rate
Error
3007670x02FF3000%15350x05FF3000%
6003830x017F6000%7670x02FF6000%
9002550x00FF9000%5110x01FF9000%
12001910x00BF12000%3830x017F12000%
18001270x007F18000%2550x00FF18000%
2400950x005F24000%1910x00BF24000%
3600630x003F36000%1270x007F36000%
4800470x002F48000%950x005F48000%
9600230x001796000%470x002F96000%
14.4 K150x000F14.4 K0%310x001F14.4 K0%
19.2 K110x000B19.2 K0%230x001719.2 K0%
28.8 K70x000728.8 K0%150x000F28.8 K0%
33.6 K60x000632.914 K-2%130x000D32.914 K-2%
38.4 K50x000538.4 K0%110x000B38.4 K0%
56 K30x000357.6 K2.9%70x000757.6 K2.9%
57.6 K30x000357.6 K0%70x000757.6 K0%
76.8 K20x000276.8 K0%50x000576.8 K0%
115.2 K10x0001115.2 K0%30x0003115.2 K0%
128 K10x0001115.2 K-10%30x0003115.2 K-10%
153.6 K10x0001115.2 K-25%20x0002153.6 K0%
230.4 K00x0000230.4 K0%10x0001230.4 K0%
fCPU = 4 MHz
Bit RateU2Xn = 0U2Xn = 1
UBRR
(dec)
UBRR
(hex)
Actual
Bit Rate
ErrorUBRR
(dec)
UBRR
(hex)
Actual
Bit Rate
Error
3008320x0340300.120%16660x0682299.94-0%
6004160x01A0599.52-0.1%8320x0340600.240%
9002770x0115899.28-0.1%5550x022B899.28-0.1%
12002070x00CF1201.920.2%4160x01A01199.04-0.1%
18001380x008A1798.56-0.1%2770x01151798.56-0.1%
24001030x00672403.850.2%2070x00CF2403.850.2%
3600680x00443623.190.6%1380x008A3597.12-0.1%
4800510x00334807.690.2%1030x00674807.690.2%
9600250x00199615.380.2%510x00339615.380.2%
14.4 K160x001014.706 K2.1%340x002214.286 K-0.8%
19.2 K120x000C19.231 K0.2%250x001919.231 K0.2%
28.8 K80x000827.778 K-3.5%160x001029.412 K2.1%
33.6 K60x000635.714 K6.3%140x000E33.333 K-0.8%
38.4 K60x000635.714 K-7%120x000C38.462 K0.2%
56 K30x000362.5 K11.6%80x000855.556 K-0.8%
57.6 K30x000362.5 K8.5%80x000855.556 K-3.5%
76.8 K20x000283.333 K8.5%60x000671.429 K-7%
115.2 K10x0001125 K8.5%30x0003125 K8.5%
128 K10x0001125 K-2.3%30x0003125 K-2.3%
153.6 K10x0001125 K-18.6%20x0002166.667 K8.5%
230.4 K00x0000250 K8.5%10x0001250 K8.5%
fCPU = 7.3728 MHz
Bit RateU2Xn = 0U2Xn = 1
UBRR
(dec)
UBRR
(hex)
Actual
Bit Rate
ErrorUBRR
(dec)
UBRR
(hex)
Actual
Bit Rate
Error
30015350x05FF3000%30710x0BFF3000%
6007670x02FF6000%15350x05FF6000%
9005110x01FF9000%10230x03FF9000%
12003830x017F12000%7670x02FF12000%
18002550x00FF18000%5110x01FF18000%
24001910x00BF24000%3830x017F24000%
36001270x007F36000%2550x00FF36000%
4800950x005F48000%1910x00BF48000%
9600470x002F96000%950x005F96000%
14.4 K310x001F14.4 K0%630x003F14.4 K0%
19.2 K230x001719.2 K0%470x002F19.2 K0%
28.8 K150x000F28.8 K0%310x001F28.8 K0%
33.6 K130x000D32.914 K-2%260x001A34.133 K1.6%
38.4 K110x000B38.4 K0%230x001738.4 K0%
56 K70x000757.6 K2.9%150x000F57.6 K2.9%
57.6 K70x000757.6 K0%150x000F57.6 K0%
76.8 K50x000576.8 K0%110x000B76.8 K0%
115.2 K30x0003115.2 K0%70x0007115.2 K0%
128 K30x0003115.2 K-10%60x0006131.657 K2.9%
153.6 K20x0002153.6 K0%50x0005153.6 K0%
230.4 K10x0001230.4 K0%30x0003230.4 K0%
fCPU = 8 MHz
Bit RateU2Xn = 0U2Xn = 1
UBRR
(dec)
UBRR
(hex)
Actual
Bit Rate
ErrorUBRR
(dec)
UBRR
(hex)
Actual
Bit Rate
Error
30016660x0682299.94-0%33320x0D04300.030%
6008320x0340600.240%16660x0682599.88-0%
9005550x022B899.28-0.1%11100x0456900.090%
12004160x01A01199.04-0.1%8320x03401200.480%
18002770x01151798.56-0.1%5550x022B1798.56-0.1%
24002070x00CF2403.850.2%4160x01A02398.08-0.1%
36001380x008A3597.12-0.1%2770x01153597.12-0.1%
48001030x00674807.690.2%2070x00CF4807.690.2%
9600510x00339615.380.2%1030x00679615.380.2%
14.4 K340x002214.286 K-0.8%680x004414.493 K0.6%
19.2 K250x001919.231 K0.2%510x003319.231 K0.2%
28.8 K160x001029.412 K2.1%340x002228.571 K-0.8%
33.6 K140x000E33.333 K-0.8%290x001D33.333 K-0.8%
38.4 K120x000C38.462 K0.2%250x001938.462 K0.2%
56 K80x000855.556 K-0.8%170x001155.556 K-0.8%
57.6 K80x000855.556 K-3.5%160x001058.824 K2.1%
76.8 K60x000671.429 K-7%120x000C76.923 K0.2%
115.2 K30x0003125 K8.5%80x0008111.111 K-3.5%
128 K30x0003125 K-2.3%70x0007125 K-2.3%
153.6 K20x0002166.667 K8.5%60x0006142.857 K-7%
230.4 K10x0001250 K8.5%30x0003250 K8.5%
fCPU = 10 MHz
Bit RateU2Xn = 0U2Xn = 1
UBRR
(dec)
UBRR
(hex)
Actual
Bit Rate
ErrorUBRR
(dec)
UBRR
(hex)
Actual
Bit Rate
Error
30020820x0822300.050%41660x1046299.98-0%
60010410x0411599.81-0%20820x0822600.10%
9006930x02B5900.580.1%13880x056C899.93-0%
12005200x02081199.62-0%10410x04111199.62-0%
18003460x015A1801.150.1%6930x02B51801.150.1%
24002590x01032403.850.2%5200x02082399.23-0%
36001730x00AD3591.95-0.2%3460x015A3602.310.1%
48001290x00814807.690.2%2590x01034807.690.2%
9600640x00409615.380.2%1290x00819615.380.2%
14.4 K420x002A14.535 K0.9%860x005614.368 K-0.2%
19.2 K320x002018.939 K-1.4%640x004019.231 K0.2%
28.8 K210x001528.409 K-1.4%420x002A29.07 K0.9%
33.6 K180x001232.895 K-2.1%360x002433.784 K0.5%
38.4 K150x000F39.063 K1.7%320x002037.879 K-1.4%
56 K100x000A56.818 K1.5%210x001556.818 K1.5%
57.6 K100x000A56.818 K-1.4%210x001556.818 K-1.4%
76.8 K70x000778.125 K1.7%150x000F78.125 K1.7%
115.2 K40x0004125 K8.5%100x000A113.636 K-1.4%
128 K40x0004125 K-2.3%90x0009125 K-2.3%
153.6 K30x0003156.25 K1.7%70x0007156.25 K1.7%
230.4 K20x0002208.333 K-9.6%40x0004250 K8.5%
fCPU = 11.0592 MHz
Bit RateU2Xn = 0U2Xn = 1
UBRR
(dec)
UBRR
(hex)
Actual
Bit Rate
ErrorUBRR
(dec)
UBRR
(hex)
Actual
Bit Rate
Error
30023030x08FF3000%46070x11FF3000%
60011510x047F6000%23030x08FF6000%
9007670x02FF9000%15350x05FF9000%
12005750x023F12000%11510x047F12000%
18003830x017F18000%7670x02FF18000%
24002870x011F24000%5750x023F24000%
36001910x00BF36000%3830x017F36000%
48001430x008F48000%2870x011F48000%
9600710x004796000%1430x008F96000%
14.4 K470x002F14.4 K0%950x005F14.4 K0%
19.2 K350x002319.2 K0%710x004719.2 K0%
28.8 K230x001728.8 K0%470x002F28.8 K0%
33.6 K200x001432.914 K-2%400x002833.717 K0.3%
38.4 K170x001138.4 K0%350x002338.4 K0%
56 K110x000B57.6 K2.9%240x001855.296 K-1.3%
57.6 K110x000B57.6 K0%230x001757.6 K0%
76.8 K80x000876.8 K0%170x001176.8 K0%
115.2 K50x0005115.2 K0%110x000B115.2 K0%
128 K40x0004138.24 K8%100x000A125.673 K-1.8%
153.6 K40x0004138.24 K-10%80x0008153.6 K0%
230.4 K20x0002230.4 K0%50x0005230.4 K0%
fCPU = 14.7456 MHz
Bit RateU2Xn = 0U2Xn = 1
UBRR
(dec)
UBRR
(hex)
Actual
Bit Rate
ErrorUBRR
(dec)
UBRR
(hex)
Actual
Bit Rate
Error
30030710x0BFF3000%61430x17FF3000%
60015350x05FF6000%30710x0BFF6000%
90010230x03FF9000%20470x07FF9000%
12007670x02FF12000%15350x05FF12000%
18005110x01FF18000%10230x03FF18000%
24003830x017F24000%7670x02FF24000%
36002550x00FF36000%5110x01FF36000%
48001910x00BF48000%3830x017F48000%
9600950x005F96000%1910x00BF96000%
14.4 K630x003F14.4 K0%1270x007F14.4 K0%
19.2 K470x002F19.2 K0%950x005F19.2 K0%
28.8 K310x001F28.8 K0%630x003F28.8 K0%
33.6 K260x001A34.133 K1.6%540x003633.513 K-0.3%
38.4 K230x001738.4 K0%470x002F38.4 K0%
56 K150x000F57.6 K2.9%320x002055.855 K-0.3%
57.6 K150x000F57.6 K0%310x001F57.6 K0%
76.8 K110x000B76.8 K0%230x001776.8 K0%
115.2 K70x0007115.2 K0%150x000F115.2 K0%
128 K60x0006131.657 K2.9%130x000D131.657 K2.9%
153.6 K50x0005153.6 K0%110x000B153.6 K0%
230.4 K30x0003230.4 K0%70x0007230.4 K0%
fCPU = 16 MHz
Bit RateU2Xn = 0U2Xn = 1
UBRR
(dec)
UBRR
(hex)
Actual
Bit Rate
ErrorUBRR
(dec)
UBRR
(hex)
Actual
Bit Rate
Error
30033320x0D04300.030%66660x1A0A299.99-0%
60016660x0682599.88-0%33320x0D04600.060%
90011100x0456900.090%22210x08AD900.090%
12008320x03401200.480%16660x06821199.76-0%
18005550x022B1798.56-0.1%11100x04561800.180%
24004160x01A02398.08-0.1%8320x03402400.960%
36002770x01153597.12-0.1%5550x022B3597.12-0.1%
48002070x00CF4807.690.2%4160x01A04796.16-0.1%
96001030x00679615.380.2%2070x00CF9615.380.2%
14.4 K680x004414.493 K0.6%1380x008A14.388 K-0.1%
19.2 K510x003319.231 K0.2%1030x006719.231 K0.2%
28.8 K340x002228.571 K-0.8%680x004428.986 K0.6%
33.6 K290x001D33.333 K-0.8%590x003B33.333 K-0.8%
38.4 K250x001938.462 K0.2%510x003338.462 K0.2%
56 K170x001155.556 K-0.8%350x002355.556 K-0.8%
57.6 K160x001058.824 K2.1%340x002257.143 K-0.8%
76.8 K120x000C76.923 K0.2%250x001976.923 K0.2%
115.2 K80x0008111.111 K-3.5%160x0010117.647 K2.1%
128 K70x0007125 K-2.3%150x000F125 K-2.3%
153.6 K60x0006142.857 K-7%120x000C153.846 K0.2%
230.4 K30x0003250 K8.5%80x0008222.222 K-3.5%
fCPU = 18.432 MHz
Bit RateU2Xn = 0U2Xn = 1
UBRR
(dec)
UBRR
(hex)
Actual
Bit Rate
ErrorUBRR
(dec)
UBRR
(hex)
Actual
Bit Rate
Error
30038390x0EFF3000%76790x1DFF3000%
60019190x077F6000%38390x0EFF6000%
90012790x04FF9000%25590x09FF9000%
12009590x03BF12000%19190x077F12000%
18006390x027F18000%12790x04FF18000%
24004790x01DF24000%9590x03BF24000%
36003190x013F36000%6390x027F36000%
48002390x00EF48000%4790x01DF48000%
96001190x007796000%2390x00EF96000%
14.4 K790x004F14.4 K0%1590x009F14.4 K0%
19.2 K590x003B19.2 K0%1190x007719.2 K0%
28.8 K390x002728.8 K0%790x004F28.8 K0%
33.6 K330x002133.882 K0.8%680x004433.391 K-0.6%
38.4 K290x001D38.4 K0%590x003B38.4 K0%
56 K200x001454.857 K-2%400x002856.195 K0.3%
57.6 K190x001357.6 K0%390x002757.6 K0%
76.8 K140x000E76.8 K0%290x001D76.8 K0%
115.2 K90x0009115.2 K0%190x0013115.2 K0%
128 K80x0008128 K0%170x0011128 K0%
153.6 K70x0007144 K-6.3%140x000E153.6 K0%
230.4 K40x0004230.4 K0%90x0009230.4 K0%
fCPU = 20 MHz
Bit RateU2Xn = 0U2Xn = 1
UBRR
(dec)
UBRR
(hex)
Actual
Bit Rate
ErrorUBRR
(dec)
UBRR
(hex)
Actual
Bit Rate
Error
30041660x1046299.98-0%83320x208C300.010%
60020820x0822600.10%41660x1046599.95-0%
90013880x056C899.93-0%27770x0AD9899.93-0%
120010410x04111199.62-0%20820x08221200.190%
18006930x02B51801.150.1%13880x056C1799.86-0%
24005200x02082399.23-0%10410x04112399.23-0%
36003460x015A3602.310.1%6930x02B53602.310.1%
48002590x01034807.690.2%5200x02084798.46-0%
96001290x00819615.380.2%2590x01039615.380.2%
14.4 K860x005614.368 K-0.2%1730x00AD14.368 K-0.2%
19.2 K640x004019.231 K0.2%1290x008119.231 K0.2%
28.8 K420x002A29.07 K0.9%860x005628.736 K-0.2%
33.6 K360x002433.784 K0.5%730x004933.784 K0.5%
38.4 K320x002037.879 K-1.4%640x004038.462 K0.2%
56 K210x001556.818 K1.5%440x002C55.556 K-0.8%
57.6 K210x001556.818 K-1.4%420x002A58.14 K0.9%
76.8 K150x000F78.125 K1.7%320x002075.758 K-1.4%
115.2 K100x000A113.636 K-1.4%210x0015113.636 K-1.4%
128 K90x0009125 K-2.3%190x0013125 K-2.3%
153.6 K70x0007156.25 K1.7%150x000F156.25 K1.7%
230.4 K40x0004250 K8.5%100x000A227.273 K-1.4%

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.

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.

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