This info is often needed, so put it in a stored procedure ...
use system;
drop procedure if exists tsiz;
create procedure tsiz( db varchar(64), tbl varchar(64) )
select
concat(round(sum(table_rows)/1000000,2),'m') rows,
concat(round(sum(data_length)/(1024*1024*1024),2),'g') data,
concat(round(sum(index_length)/(1024*1024*1024),2),'g') idx,
concat(round(sum(data_length+index_length)/(1024*1024*1024),2),'g') total_size,
round(sum(index_length)/sum(data_length+index_length),2) idxfrac
from information_schema.tables
where table_schema=db and table_name=tbl;