Simple syrup usually stays good in the fridge for about 2–4 weeks, but the exact time depends on the sugar ratio and whether it’s flavored.

How long it’s good in the fridge

  • Standard 1:1 simple syrup (1 part sugar, 1 part water)
    • Common guidance: about 2 weeks in the fridge.
* Many home bakers and bartenders safely stretch it to around 1 month in a clean, airtight container.
  • Rich simple syrup (2:1 sugar to water)
    • Higher sugar means a longer life: often 1–6 months refrigerated if stored properly.
  • Flavored syrups (with fruit, herbs, juice)
    • Shorter life: usually 1–2 weeks in the fridge because the added ingredients spoil faster.

How to tell if it’s gone bad

Even if you’re inside the “normal” time window, always check:

  • Cloudiness, haze, or separation that wasn’t there before.
  • Mold spots or a wispy “floaty” layer.
  • Off smells or sour/fermented notes instead of a clean sweet smell.

If you see any of these, toss it—simple syrup is cheap and quick to remake.

Storage tips to make it last longer

  • Use a very clean, airtight glass jar or bottle (like a mason jar or swing-top).
  • Keep it in the coldest part of the fridge, not the door.
  • Don’t leave it out on the counter for long; pour what you need and put it back.
  • For longer storage, you can freeze simple syrup for up to about 3 months, then thaw in the fridge before using.

Quick example

If you made a plain 1:1 syrup last week, stored it in a clean jar in the fridge and it still looks clear, smells neutral-sweet, and has no floaties, it’s almost certainly fine to use now.

TL;DR:
Plain 1:1 simple syrup: safest to use within 2 weeks, often fine up to about a month if clear and refrigerated. Rich 2:1: can last 1–6 months. Flavored: aim for 1–2 weeks max. Always discard at any sign of cloudiness, off smell, or mold.

Information gathered from public forums or data available on the internet and portrayed here.