Reading Time on Medium & Substack
One platform calculates it for you; the other doesn't have a field at all.
Medium: automatic, based on its own formula
Medium calculates and displays reading time on every story automatically — you can't turn it off or edit it directly. Medium's publicly discussed formula counts words plus an added time penalty for each image (roughly 12 seconds for the first image, decreasing for subsequent ones, capped after a handful of images), then divides by approximately 265 WPM, close to but not identical to ReadMetric's 238 WPM default. If your Medium estimate looks different from ReadMetric's, that formula difference — not an error — is usually why.
Substack: no native field, use a manual workaround
Substack does not display an automatic reading-time estimate on posts. The practical workaround is to calculate it yourself and add it as plain text at the top of the post, right after the title — for example, "6 min read" as the first line before your introduction. Paste your draft into the ReadMetric calculator before publishing to get the number.
Keeping the estimate consistent across platforms
If you cross-post the same article to your own site, Medium and Substack, the displayed reading time may differ slightly across each due to different formulas (or none at all on Substack). Where you control the number — your own site and Substack — use the same WPM assumption (238 is a solid default) so returning readers see consistent estimates. See our reading time & SEO guide for why that consistency matters.