What is the 100-mile rule in polyamory?

The 100-mile rule names an agreement whose condition is geography: the couple are monogamous in ordinary life and open only when one of them is far from home. The term appears in Franklin Veaux’s 2010 Map of Non-Monogamy, a chart of relationship structures covered by the outlet Mic in 2015, where the rule is expressed in the chart’s own words: “We’re monogamous. Except when he’s on the road.” Read that phrasing closely — it describes a couple who treat distance as the trigger, and it gives no reason why.

A community wiki entry published under the heading “Geographical Non-Monogamy or The 100 Mile Rule” defines the same idea from the other direction: partners “permit one another to have other sexual partners” “while they are physically apart”, with long-distance relationships, business trips and vacations apart given as the examples, and an understanding — “not necessarily for everyone” — that the relationship becomes monogamous again when the two are together (LGBTQIA+ Wiki). The two definitions agree on the mechanism: the permission is temporary and tied to being away. They differ in emphasis — one describes a couple who are monogamous except while one of them travels, the other an openness that switches off when the partners reunite — and that difference is the honest headline: the label is informal, so published sources describe it differently.

The label is not a formal category. It is not one of the polyamory terms this library’s glossary defines — compersion, metamour, NRE, kitchen-table and parallel polyamory all have entries; this label has none — and the wiki entry’s sourcing for the term’s history is a single Urban Dictionary submission, which is thin even for a wiki. None of that makes the arrangement unreal: couples write all kinds of conditions into open agreements, and a geographic condition is no stranger than any other. It does mean that if a partner, a profile or a forum post uses “the 100-mile rule,” the useful question is what it means for them, not which of the two published definitions is correct. The answer on setting rules as a couple covers how to write an agreement that says what you actually mean.

There is also a distinction the label cannot make for you, and it is the one that matters. If both people know about the arrangement and keep to it, a distance rule is simply one term in an open agreement, and the answer on DADT covers the version whose terms include not sharing details, along with why it draws consent objections — agreeing to the existence of encounters is not the same as agreeing to their specifics. If the encounters are hidden, then whatever the label, there is no agreement: non-monogamy without knowledge and consent is not an arrangement, and the answers on open relationships and on monogamy versus non-monogamy describe where that line sits. Distance changes nothing about safer sex either: being away from home is not a protection, so the Play Safe answers on condoms and STI testing apply wherever an encounter happens.

This answer publishes no prevalence figure, because no source we could find offers one — the two definitions above describe the arrangement, not how many couples use it. If the question behind the question is whether a distance-based agreement is right for you, the test is the one every rule faces: both people should want it, say so in words rather than assuming, and be able to revisit it rather than treating it as settled. JoinTheSwing is pre-launch: new registration remains closed until the coordinated native-app release is approved, and the public answers library and free launch list are open meanwhile.