The mathematics in verse 23 is NOT in error.  Why?  Because of verse 26,  ".....HAND BREADTH THICK..."

"1 Kings 7:[26] And it was an HAND BREADTH THICK[#02947 tephach], and the BRIM[#08193 saphah] thereof was wrought like the brim of a cup, with  flowers of lilies: it contained two thousand baths."  First, a cubit  (strongs #0520 = 'ammah') is defined as approximately 18 in. For the sake of this illustration, 18 inches will be used.

      The rub with this verse 23 is that it does not state how thick the brim is! So here is the mathematics to prove that
      verse 26 is accurate ("...the hand breadth thick...").

      PI = 3.14159 (approximately), the diameter must be solved to account for the width of the brim, so therefore we must
      solve for "d"......in doing this we get,

      30 cubits = 30 x 18 inches = 540 inches it total circumference. 540 inches DIVIDED by PI = 171.8874 inches.

      Now, since it is now known that DIAMETER is 171.8874, we must now subtract the different between the
      breadth thickness of EACH SIDE. In other words, when measuring the diameter of an tank or container that has
      substantial thickness, the thickness must be accounted for TWICE. Once for the first edge, then ONCE MORE for the
      opposite edge. Therefore we get,

      10 cubits = 180 inches - 171.8874 inches = 8.1126 inches.

      Now divide 8.1126 by TWO, we get 4.0563 inches. NOW GET OUT A RULER AND MEASURE THE
      BREADTH OF YOUR HAND!!!!!
 

     CUBIT = 0520 ammah {am-maw'}

      prolonged from 0517; TWOT - 115c; n f

      AV - cubit 242, measure 1, post 1, not translated 1; 245

      1) cubit - a measure of distance (the forearm), roughly 18 in (.5m).
      There are several cubits used in the OT, the cubit of a man or common
      cubit (Dt 3.11), the legal cubit or cubit of the sanctuary (Eze 40.5)
      plus others. See a Bible Dictionary for a complete treatment
 

     HAND BREADTH = 02947 tephach {tay'-fakh}

      from 02946; TWOT - 818b; n m

     AV - hand breath 3, coping 1; 4

     1) span, width of the hand, hand breadth
     1a) a unit of measurement, measurement of length
     2) coping (an architectural term)

     BRIM = 08193 saphah {saw-faw'} or (in dual and plural) sepheth {sef-eth'}

     probably from 05595 or 08192 through the idea of termination (compare
     05490); TWOT - 2278a; n f

    AV - lip 112, bank 10, brim 8, edge 8, language 7, speech 6, shore 6,
     brink 5, border 3, side 3, prating 2, vain 2, misc 4; 176

     1) lip, language, speech, shore, bank, brink, brim, side, edge,
     border, binding
     1a) lip (as body part)
     1b) language
     1c) edge, shore, bank (of cup, sea, river, etc)

 
      [24] And under the brim of it round about there were knops compassing it, ten in a cubit, compassing the sea round
      about: the knops were cast in two rows, when it was cast.
      [25] It stood upon twelve oxen, three looking toward the north, and three looking toward the west, and three looking
      toward  the south, and three looking toward the east: and the sea was set above upon them, and all their hinder parts were
      inward.
      [26] And it was an HAND BREADTH THICK, and the BRIM thereof was wrought like the brim of a cup, with
      flowers of lilies: it contained two thousand baths.
 
 

 
      
 
  D2  = the measured diameter between
                                                                                                                the extreme OUTER points of the rim
                                                                                                                at the very top of the molten sea tub.
 
 
 

Table of computation of Pi from 2000 BC to now