Typical adult lifespan: 15–25 days, up to two months (UF/IFAS); up to 3 weeks (Texas A&M AgriLife). By temperature: median 34–43 days at 20 °C, 21–24 days at 25 °C and 10–12 days at 35 °C (Fletcher et al. 1990). Without food: only 2–3 days (UF/IFAS). Males vs females: females usually live a few days longer.
How long do house flies live?
About two to four weeks. University of Florida entomologists say adult house flies "usually live 15 to 25 days, but may live up to two months" (UF/IFAS), and Texas A&M AgriLife Extension puts it at up to three weeks. That's the house fly lifespan for the winged adult; the egg, maggot and pupa stages add about a week or two before it.
So how long do house flies live for in your kitchen? It depends on three things:
- Temperature: they "live longer at cooler temperatures" (UF/IFAS). In the lab, the median female lived 43 days at 20 °C (68 °F) but only 10 days at 35 °C (95 °F) (Fletcher et al. 1990).
- Food: "Longevity is enhanced by availability of suitable food, especially sugar"; without food they survive only about two to three days (UF/IFAS).
- Sex: females outlive males in mild weather; in great heat the difference disappears.
People phrase the question many ways — how long does a house fly live, how long can house flies live, or simply "how long to house flies live" — and the answer is the same range. How long can a house fly live at the very most? Up to about two months, in cool conditions with plenty of sugar (UF/IFAS). And how long do common house flies live compared with other flies in the house? A little shorter than kitchen fruit flies, and a little longer than most mosquitoes — see the comparison below.
Average life of a house fly
The average life of a housefly — or the average lifespan of a housefly, if you prefer — in a lab at 25 °C (77 °F) — the temperature of a warm room — is a median of 24 days for females and 21 days for males (Fletcher et al. 1990). That fits UF/IFAS's 15–25 days. The common house fly life span in a real home is usually shorter, because flies are swatted, trapped, caught by spiders or shut outside. So how long does the average housefly live? About three weeks, give or take a week. That's the life span of a house fly most people will see, and the "average life of house fly" figure the calculator starts from.
Why a house fly's lifespan matters in a kitchen
Two to four weeks is a long time for an insect that visits both the bin and the dinner table. House flies don't bite, but UF/IFAS explains that they pick up disease-causing organisms "from garbage, sewage and other sources of filth" and carry them to food on their mouthparts, their feet and body, and in their vomit and droppings. Some pathogens can survive in a fly's mouthparts or gut "for several days" before being passed on. The bacteria UF/IFAS lists include Salmonella, Shigella, Campylobacter and E. coli, and house flies are most often linked to outbreaks of diarrhoea and shigellosis where sanitation is poor.
That's why a fly's lifespan matters: every extra day is another round of landings. In homes the tolerance is, as UF/IFAS puts it, "very low", and the practical answer is the same as for any fly problem — cover food, keep bins closed and remove the waste they breed in. This is general background, not medical advice; if you're worried about food safety or illness, talk to a health professional.
In short: how long house flies live is a matter of weeks, not days — but much less than the months a hibernating cluster fly spends in your attic (see cluster flies).
House fly lifespan by temperature
House flies are cold-blooded, so warmth speeds up their whole body clock. In a study at four constant temperatures, the time for half of the adult flies to die fell steadily as the temperature rose (Fletcher et al. 1990):
| Temperature | Females | Males | Eggs per female |
|---|---|---|---|
| 20 °C (68 °F) | 43 days | 34 days | 184 |
| 22 °C (71.6 °F) (calculated) | 36 days | 29 days | — |
| 25 °C (77 °F) | 24 days | 21 days | 729 |
| 28 °C (82.4 °F) (calculated) | 20 days | 18 days | — |
| 30 °C (86 °F) | 17 days | 15 days | 709 |
| 35 °C (95 °F) | 10 days | 12 days | 506 |
Rows marked "calculated" sit between the measured temperatures. Females laid the most eggs at 25–30 °C (729 and 709) and far fewer at 20 °C (184), which matches UF/IFAS: maximum egg production at intermediate temperatures, 25–30 °C.
Do flies live longer in summer?
No — individual flies live shorter lives in summer heat. A female house fly at 30 °C (86 °F) has a median life of 17 days, against 43 days at 20 °C. Summer brings more flies because each generation develops faster in warm weather (as little as seven to ten days, UF/IFAS) and females lay more eggs, not because the adults live longer. That's the same trade-off fruit flies and mosquitoes show.
House fly life expectancy: males vs females
House fly life expectancy differs a little between the sexes. At 20 °C, the median female lived 43 days and the median male 34 days; at 25 °C, 24 days against 21 days; at 30 °C, 17 days against 15 days. At 35 °C the order flips: males lived 12 days and females 10 days (Fletcher et al. 1990).
Telling them apart is easy with a close look: in males the eyes almost touch, while females have a wider space between them, and the female is usually larger (UF/IFAS). The calculator's "Not sure" option shows the range covering both sexes, and the comparison bars make the male vs female house fly lifespan gap easy to see at any temperature.
Houseflies' lifespan and egg laying
A female's life is built around egg laying. She needs food before she'll mate, and needs protein to make eggs; laying starts 4–20 days after mating (UF/IFAS). She can lay up to 500 eggs in several batches of 75–150 (UF/IFAS); the University of New Hampshire gives 350–900 in a lifetime. Those details belong to the house fly life cycle, which tracks eggs, maggots and pupae with dates. The houseflies lifespan figures on this page are for the adult flies only.
How long do flies live in your house?
A house fly indoors lives about as long as one outdoors — two to four weeks — if it can find food. How long do flies live in your house really depends on what's left out: crumbs, spills, fruit, pet food and an open bin are all fly food, and sugar especially lengthens their lives (UF/IFAS). In a clean room with nothing to eat, a fly lasts only two or three days.
So how long can a fly live in your house? Up to a few weeks with food, or a couple of days without. A few practical points:
- How long do house flies live indoors at night? They're inactive after dark and rest on ceilings, beams and overhead wires (UF/IFAS), which is why you often find them high up in the morning.
- How long do flies live in the house in winter? Some adults survive the winter in heated buildings (UNH Extension) — a warm home is mild weather for a fly.
- How long can flies live in your house if new ones keep appearing? Indefinitely, as a group: flies seen for weeks are usually a series of new adults hatching from a bin, compost caddy or pet waste nearby, not one old fly.
The life span of a fly in a house also depends on the temperature you keep: the calculator's comparison bars show how much longer a fly lives in a cool room than a warm one. Put together, the fly lifespan in house conditions is roughly 15–25 days with food (UF/IFAS) — and if flies keep coming, the house fly life cycle calculator shows how quickly a bin can produce new ones.
How long can a fly live in a house with no way out?
If it's trapped between a window and a screen with no food or water, only a couple of days. How long can a fly live in a house that's been closed up — say, while you're away? With crumbs and water around, the full two to four weeks; in a spotless, closed home, two to three days.
How long can a fly live without food or water?
About two to three days without food: "Without food, they survive only about two to three days" (UF/IFAS). That figure doesn't come with a temperature, so the calculator doesn't adjust it; flies in a hot, dry room may die sooner.
Without water, we found no study that timed house flies with food but nothing to drink, so we don't give a separate figure. In practice a fly's food is often wet — spills, fruit, rubbish, pet food — and the two-to-three-day starvation figure is the best sourced estimate for a fly with neither.
Sugar matters more than people expect. UF/IFAS notes that access to manure does not lengthen adult life — flies need sugary food to live their full span. That's why a fly in a room with a fruit bowl outlives one in an empty spare room by weeks.
Why flies die on windowsills
Why do flies die on windowsills? Most of the dead flies that collect on windowsills in autumn, winter and early spring are cluster flies, not house flies. Cluster flies spend the winter in walls and attics; when they wake, they "go to the nearest light source, such as a window or glass door" and "tend to die rather quickly" (Montana State University). Homes are "usually too hot and dry for their survival", and they're often seen "spinning on their sides on windowsills or floors while buzzing loudly" (Virginia Tech).
House flies die there too, for a simpler reason: a fly trapped against glass can't reach food, and without food it lasts only two to three days (UF/IFAS). Vacuum dead flies up and empty the vacuum straight away — dead flies attract carpet beetles, whose larvae feed on dead insects (Virginia Tech).
Do house flies die in winter?
Do flies die in winter? Outdoors, most adult house flies do; the species survives as pupae in manure piles and other organic debris, while "some adults can survive the winter in heated buildings" (UNH Extension). In temperate regions there can be 10–12 generations a year, so numbers rebuild quickly in spring (UF/IFAS). For winter flies that gather in attics, see the cluster fly calculator.
House flies vs fruit flies vs mosquitoes: lifespan compared
These three are the insects most people find flying around the house, and their lives are surprisingly similar in length:
| Insect | Typical adult lifespan | With no food |
|---|---|---|
| House fly (Musca domestica) | Usually 15–25 days, up to 2 months (UF/IFAS); median 21–24 days at 25 °C (Fletcher et al. 1990) | 2–3 days (UF/IFAS) |
| Fruit fly — fruit fly lifespan calculator | Around a month at home (University of Kentucky); 38–63 days in the lab at 25 °C | About 63–70 hours at 21 °C with water (Da Lage et al. 1989) |
| Mosquito — mosquito lifespan calculator | Females usually under 2 weeks, males under a week outdoors (Coachella Valley MVCD); females 19–67 days in the lab at 25 °C | 2–12 days with water (Manda et al. 2007) |
All three live longest in mild weather and shortest in heat, and all three die within days without food. The big difference is breeding: house flies breed in garbage and manure, fruit flies in fermenting fruit and drains, and mosquitoes in standing water. How long does a fly live is only half the story — how long do flies live for as a problem depends on finding where they breed.
How this house fly lifespan calculator works
- Lifespan by temperature: the median adult lifespan for each sex at 20, 25, 30 and 35 °C, calculated from the median mortality rates in Fletcher et al. (1990) (days to 50% mortality = 1 ÷ rate), with straight lines between. "Not sure" spans both sexes.
- Comparison bars show the same fly 5 °C cooler and warmer, within 20–35 °C.
- No food or water: UF/IFAS's two to three days, which doesn't vary with temperature.
- Days since you first saw it becomes a percentage of the typical life at your temperature — or of the 2–3 days a fly survives without food.
- Egg to adult at your temperature uses the same model as our house fly life cycle calculator (Liu et al. 2026), so the two pages always agree.
Flies below 20 °C live longer (UF/IFAS), but we found no measured lifespan below 20 °C, so the calculator asks for a temperature from 20 to 35 °C rather than guessing.
Frequently asked questions
How long do house flies live?
Usually 15–25 days and up to two months (UF/IFAS); Texas A&M says up to 3 weeks. Cooler temperatures and sugar help them live longer.
How long does a house fly live indoors?
About as long as outdoors — 2 to 4 weeks — if it can find food. With no food, only 2–3 days (UF/IFAS).
What is the average life of a house fly?
About three weeks. In the lab at 25 °C, the median female lived 24 days and the median male 21 days (Fletcher et al. 1990).
How long can a fly live without food?
About two to three days (UF/IFAS).
How long can a fly live without water?
We found no study that timed house flies with food but no water; without food or water, two to three days is the best sourced figure.
Do house flies live longer in summer?
No — heat shortens their lives: about 17 days for females at 30 °C against 43 days at 20 °C (Fletcher et al. 1990). There are more flies in summer because they breed faster.
Do female house flies live longer than males?
Usually: at 25 °C the median female lived 24 days and the male 21 days. At 35 °C males lived slightly longer (Fletcher et al. 1990).
How long do flies live in your house in winter?
Some adults survive the winter in heated buildings (UNH Extension). Outdoors, house flies survive cold as pupae in organic debris.
Why are there dead flies on my windowsill?
Usually cluster flies, which head for the light when they wake from hibernation and die quickly in warm, dry homes (Montana State; Virginia Tech). Trapped house flies starve within 2–3 days.
How long does a fly live compared with a fruit fly?
A house fly usually lives 15–25 days (UF/IFAS); a fruit fly around a month in a home (University of Kentucky).
How long do flies live compared with mosquitoes?
Most female mosquitoes live under 2 weeks and males under a week (Coachella Valley MVCD) — a little shorter than house flies.
How long can house flies live at most?
Up to about two months (UF/IFAS), in cool conditions with plenty of sugar.
Why do I keep seeing flies for weeks?
New flies are hatching from a nearby breeding site, such as a bin, compost or pet waste. The whole life cycle can take as little as 7–10 days (UF/IFAS).
These calculators give estimates for education. Real flies vary with strain, food, humidity and temperature. For a stubborn infestation, your local cooperative extension service can help identify the insect. We give no pesticide advice.