# Rods to Thou (rd to thou) Source: https://www.unitconvertercalculator.com/length/rods-to-thou/ **1 rd = 198000 thou** One rod equals approximately 197,929 thou (about 198,000 mils). Since 1 rod = 198 inches and 1 inch = 1,000 thou, multiply 198 by 1,000. The rod measures land; the thou measures precision engineering. They share the inch as common ancestor. ## Formula Convert Rods to Thou ## Conversion Table | Rods (rd) | Thou (thou) | |---|---| | 1.0E-5 rd | 1.98 thou | | 0.0001 rd | 19.8 thou | | 0.001 rd | 198 thou | | 0.005 rd | 990 thou | | 0.01 rd | 1980 thou | | 0.05 rd | 9900 thou | | 0.1 rd | 19800 thou | | 0.5 rd | 99000 thou | | 1 rd | 198000 thou | | 5 rd | 990000 thou | | 10 rd | 1980000 thou | | 100 rd | 19800000 thou | ## Units ### Rod (rd) Exactly 16.5 feet or 5.5 yards (5.0292 m). Also called a perch or pole. Historically used in land surveying. ### Thou (thou) One thousandth of an inch (0.0254 mm). Also called a mil in the US. Used in engineering, manufacturing, and for measuring thin materials like plastic film. ## Background A rod is about 198,000 thou. A 1-thou tolerance (25.4 um) is about 5.05 x 10-6 rods. Both units derive from the inch: the rod is 198 inches; the thou is 0.001 inches. They are distant cousins in the imperial family. ## Good to Know The thou and rod are the imperial system's precision extremes: the thou is the smallest common unit (0.001 inches); the rod is among the largest obsolete ones (198 inches). They share a common ancestor (the inch) but serve different centuries and different purposes. The inch connects them across 200,000:1. ## FAQ ### How many thou are in 1 rod? One rod contains approximately 197,929 thou (about 198,000). ### How many rods is 1 thou? One thou equals approximately 5.052 x 10-6 rods. ### Is this conversion used? Never. Land surveying and precision machining operate at completely different scales. ## Non-Frequently Asked Questions ### How many precision tolerances fit in a medieval rod? At 1 thou per tolerance band, about 198,000 tolerance widths fit in a rod. Medieval measurement was accurate to maybe 500 thou (0.5 inches). So the rod's own accuracy was about 0.25% of its length. Modern 1-thou precision is 500 times better. Progress is measured in fewer thou of error per rod of length. ### Could a machinist use a rod as a reference standard? No. A wooden rod changes length with humidity (about 500-1,000 thou over its length). A machinist's gauge block is stable to 0.1 thou. The rod is about 5,000-10,000 times less stable than a gauge block. Medieval and modern precision cannot share instruments. ### How many thou did medieval rods vary? Rods varied by about 500-1,000 thou (0.5-1 inch) between counties. This variation caused property disputes for centuries. Modern surveying instruments are accurate to about 0.5 thou (0.01 mm). The improvement from medieval rod to modern laser is about 1,000-2,000x in precision. ## Related Articles - [Why We Measure: The Deepest Urge in Human Civilisation](https://www.unitconvertercalculator.com/blog/why-we-measure) - [The Map Is Not the Territory: Why Every Measurement Is Wrong](https://www.unitconvertercalculator.com/blog/the-map-is-not-the-territory) - [Zero: The Most Dangerous Number in Measurement](https://www.unitconvertercalculator.com/blog/zero-the-most-dangerous-number-in-measurement) - [The Body as a Ruler: Every Measurement Unit That Came From Us](https://www.unitconvertercalculator.com/blog/the-body-as-a-ruler) - [The Speed of Everything: How We Measure From Glaciers to Light](https://www.unitconvertercalculator.com/blog/the-speed-of-everything) - [15 Obscure Measurement Units You've Never Heard Of (But Still Need)](https://www.unitconvertercalculator.com/blog/obscure-measurement-units-guide) - [When Measurements Go Wrong - Disasters, Blunders and Happy Accidents](https://www.unitconvertercalculator.com/blog/when-measurements-go-wrong) - [The Surprising Stories Behind Everyday Units of Measurement](https://www.unitconvertercalculator.com/blog/stories-behind-measurement-units) - [Metric vs. Imperial - The Complete Guide to the World's Two Measurement Systems](https://www.unitconvertercalculator.com/blog/metric-vs-imperial-complete-guide) - [Length & Distance Conversion Guide - Meters, Feet, Miles & Kilometers](https://www.unitconvertercalculator.com/blog/length-and-distance-guide) ## See Also - [Thou to Rods](https://www.unitconvertercalculator.com/length/thou-to-rods/)