Does the Bible Claim pi Equals Three?

Then he made the molten sea; it was round, ten cubits from brim to brim, and five cubits high. A line of thirty cubits would encircle it completely.

—1 Kings 7:23

This passage appears to be describing a circular object with a diameter of 10 cubits and a circumference of 30 cubits. If you're familiar with modern mathematics, you know that a circle with diameter 10 cubits has a circumference of 10 pi (approximately 31.4) cubits. A "line of thirty cubits" would not "encircle it completely". The measurements from the Bible would yield a value of exactly 3 for pi. So what gives?

It turns out there are several factors working against ancient peoples' ability to make the kind of precise measurements we might expect today.

First, the Tanakh (the Jewish Bible) was written before the invention of fixed-length measuring systems. Today, whether we are using feet or meters, we know that one unit is the same length as all other units with the same name. If I have a 30-meter rope, it is exactly three times as long as a 10-meter rope. But a cubit was not a uniformly defined standard of distance. It was defined, rather, by the length of the forearm, usually from the elbow to the tip of the middle finger, but sometimes from the elbow to the base of the hand, or from the elbow to the midpoint between the thumb and the little finger. And on top of all that, arm length varies from person to person. If the priests who wrote this passage had a 10-cubit rope and a 30-cubit rope, there's no guarantee that the ropes were measured using the same cubit.

The Tanakh was also written before the invention of positional numbering and decimal notation. If the measurement was a little less (or a little more) than 10, there was simply no way to describe that.

Additionally, depending on translation, we can't be certain that the 30-cubit line fit around the rim exactly, stretched tight, with both ends touching and no overlap. These measurements are by necessity approximations.

Furthermore, unlike passages that are meant to be instructional (e.g., Exodus 26:1-6), where specificity is relatively important, this one is merely descriptive. It doesn't need to be consulted by workers attempting to build the object according to spec. These measurements are meant to be used by priests, not construction workers. There's not an inherent need for great accuracy here.

And finally, this passage is not a word problem from an early geometry textbook, where the reader's job is to calculate the value of pi. Its purpose is to describe an object in the temple. For that purpose, the round numbers "10 cubits" and "30 cubits" would give most people of the time a good idea of its size.

You can find a lot of this information at Christian apologetics websites like Tekton Ministries or Answers in Genesis. These sites then conclude with an affirmation of the Bible's general credibility and trusworthiness in all matters.

Yet based on what we've seen so far, that conclusion is not merited.

As our ability to measure things more precisely has increased, we've grown accustomed to expect more precise measurements. You can see this in the apologetics sites' speculation that this object was actually 9.55 cubits measured on the inside of the rim (and thus 30 cubits in circumference) but 10 cubits to the outside of the rim. There is nothing in the Bible text to indicate this; it is based on nothing but the modern desire for precision. That, and an a priori belief that the Bible was written not by priests but by God himself (but that's another issue for another time).

But if the Bible was written by ancient priests for ancient priests, there's no reason to believe they intended to provide the precise level of detail that modern engineers might crave. If we're going to conclude the mathematics of the Bible is not faulty, it's because the Bible is not a math book and shouldn't be held to precise modern standards when it talks about math.

And if that's the case, then perhaps the same is true about other fields of study that are not central to the Bible's message. If the Bible is not a math book, it is also not a history or science book. The folks at Answers in Genesis have no problem saying the circular measurements in 1 Kings should not be taken at face value. Would it really hurt them to approach Genesis 1 the same way?