Dear Sanjeev Gupta,

In your case, the correct answer will be 3.7894(8).

In fact, your "error" to the fourth letter is not "7", but "7.68". You need to round this "error" (s.u., standard uncertaincy value) to 8 and write this s.u. to appropriate decimal letter. "3.7894(8)" means "3.7894+-0.0008", i.e. 8 is an error in last decimal letter. Note that according to the International Union of Crystallography rules, the value of s.u. should be within 2-19 limit (it is not correct to use s.u. = 1 or higher then 19). Say, 3.7894(20) should be rounded to 3.789(2) (with elimination of last letter), but 3.7894(19) should be used as is. 

Respected Konstantin,

What would be appropriate way to write these with significant digit. I am confused for writing (1) in significant digit. Please solve some example. and give reference

3.7714977 error:2.2886996E-4

9.470889 error:0.0011926953

12.295242 error:0.011106018

3.6982176 error:0.0020345047

6.520713 error:0.0049772994

It is very simple - you have to round out the "error" (estimated standard deviation) to one decimal letter (in the range of 2-9) or two decimal letters in the range of 10-19. After this, determine number of decimal letters in you numerica value.

3.7714977 error:2.2886996E-4   should be 3.7715(2)

9.470889 error:0.0011926953    --- 9.4709(12)

12.295242 error:0.011106018    ---- 12.295(11)

3.6982176 error:0.0020345047  ---- 3.698(2)

6.520713 error:0.0049772994   ----  6.521(5)

Please explain this how they calculated error how in bracket (16) came?

For example, a bond distance of 1.54249 Å with a s.u. of 0.01532 Å should be reported as 1.542(16) Å (e = 3%), and one of 2.16352 Å with a s.u. of 0.00481 Å should be reported as 2.164(5) Å (e = 10%)