There is no six-month passport validity rule. There is no international law, no treaty and no single global standard that says a passport must have six months left on it. What exists is a patchwork: each destination state sets its own entry requirement, those requirements differ from one another in ways that matter, and the entity that will actually stop you is not an immigration officer at all. It is the airline, at the check-in counter in Dhaka, before you have gone anywhere.
That is the whole answer to "mine has five months left, will I be refused". You will find out at check-in, from a carrier applying the destination's rule on the destination's behalf, and by then it is too late to do anything about it.
Why the airline is the one that refuses you
This is the part almost nothing on this subject explains, and it is the part that determines what happens to you.
Under the international arrangements that govern commercial aviation, a carrier that flies a passenger to a country where that passenger is then refused entry is responsible for carrying them back, and is generally liable for penalties imposed by the destination state as well. Airlines therefore check entry documents themselves, at check-in, and they check them conservatively. The airline is not enforcing its own rule and cannot waive one. It is protecting itself against a fine and a return flight, and a passenger who "will probably be fine" is a risk it has no reason to take.
Two consequences follow, and both are practical.
First, the check happens in Dhaka, not at the border. People imagine being turned away by a foreign immigration officer. Far more often the trip ends at a domestic check-in desk, with a non-refundable ticket and a visa that is now useless.
Second, an airline can be stricter than the destination's published rule, and it will not be less strict. Ground staff apply the version in their own system. Arguing that the embassy's page says something different is unlikely to move it, because the person in front of you does not have the authority to override their own system, and because they are the party who pays if they are wrong.
The requirement is not one rule, it is at least four shapes
When people say "six months", they are collapsing several genuinely different requirements into one number. The shapes in circulation are these, and which one applies to you is a fact about your destination, not about your passport.
Six months beyond the date of entry. The most common form, and the one the folk rule is built on. Widely used across Asia and the Gulf.
Six months beyond the intended date of departure. Stricter in effect, because it is measured from the end of your trip rather than the start. A month-long trip needs seven months on the passport under this version.
Three months beyond the intended date of departure. The shape used for the Schengen area, alongside a separate condition about how recently the passport was issued. A traveler who assumes six months everywhere over-prepares here, which costs nothing; a traveler who assumes three months everywhere gets caught elsewhere, which costs a trip.
Valid for the duration of stay only. Used by some countries, including several a Bangladeshi traveler might not expect. No margin required at all beyond the trip itself.
And underneath all of them sits a rule almost nobody states: a passport with very few blank pages left can be refused entry or refused a visa, independently of how much time is left on it. Page count and validity are two separate requirements and both are checked.
Why we are not giving you a table
Every page that ranks for this question offers a country-by-country list of validity requirements. We are not publishing one, and the reason is the point of this article.
No authority maintains a consolidated, current, official table of every country's passport validity requirement. The lists in circulation are compiled from each other, they are undated, and a passport validity rule is exactly the kind of fact that changes by administrative notice rather than by announcement. A stale table on this subject does not mislead you slightly. It costs you the ticket, because you will have read a number and stopped checking.
For this article we did not have a dated read of the destination authorities' own pages, and rather than repeat figures from secondary sites, we are telling you where the figure lives. That is the same posture this site takes whenever the authority is unreachable: name the authority, name what we do not know, and publish nothing we cannot stand behind.
Where the actual answer lives, in order of authority
One: the destination country's own immigration or foreign ministry page, and its embassy or consulate in Dhaka. This is the requirement itself. Everything else is a copy of it.
Two: the visa itself, and its issuing conditions. Some visas are issued only against a passport with a stated minimum validity, so if you hold a valid visa, the check may already have happened once. It will happen again at check-in.
Three: your airline's own passenger entry-requirements tool, usually available on the booking or check-in page. This is worth checking because it tells you the version the carrier will apply to you, which is the version that decides whether you board.
Four: your travel agent, last, and only as a prompt to go and read source one. An agent's confidence is not a source.
Two examples of how this shows up in practice on routes Bangladeshi travelers actually fly: our coverage of the Oman tourist visa for Bangladeshi applicants and of the Saudi tourist visa route both work from the issuing authority's own material and both say plainly where a figure could not be verified. Read the authority's page for validity the same way.
What to do if your passport is short
The honest sequence, with no encouragement to try your luck.
Count from the end of the trip, not the start. Work out the date you plan to leave the destination and count forward six months from there. If your expiry falls before that, treat yourself as short for every destination until you have confirmed otherwise.
Assume six months as your planning default, and verify the real figure. Six is the strictest common case, so a passport that clears it clears nearly everything. It is a planning assumption, not a fact about any specific country.
If you are short, renew before you book, not after. Bangladesh's Department of Immigration and Passports publishes its own delivery timetables and its own fee schedule, and the delivery figure moves depending on which of its pages you read and on whether police verification has come back. Renewal is the fix. Nothing else is.
Do not plan around a passport that expires mid-trip. Even where a destination technically permits entry on validity-for-duration-of-stay, an expired passport abroad is a consular problem, not a travel one, and it is a far more expensive week than a renewal.
Never fly on the assumption that an airline will make an exception. It has a financial reason not to, and the person you are asking has no authority to grant one.
The short version
There is no universal six-month rule. The requirement belongs to the country you are entering, it comes in several different shapes, and the airline at check-in in Dhaka is what enforces it against you. Six months is a good planning margin and a bad substitute for reading the destination authority's own page, on the date you are actually flying.