This key lime simple syrup recipe is bright and zesty while also being sweet and tart. It’s made by using both the juice and the zest of key limes, so it’s full of fresh lime flavor!
I’ve been making simple syrups for homemade beverages for over a decade now, and I’ve since created tons of variations of them. This syrup was inspired by a large crop of key limes from the tree in my parent’s backyard. I planted the tree in the early 2000’s, and it’s churned out pounds and pounds of key limes since then.
Citrus makes great syrups, as seen with this easy lemon syrup, so I knew key limes would make a great flavored syrup, too. It’s perfect for a variety of tropical and tiki drinks, from a classic Cuban daiquiri to a key lime margarita! It even works for making non-alcoholic drinks like a homemade key lime soda or a simple Moscow mule mocktail!
💕 why you’ll love this key lime simple syrup recipe…
🍋 bold & zesty. Key limes are tart, but not as tart as regular Persian limes, which are the most common variety available at the grocery store. They have a sweet, almost unique floral flavor to them!
🍭 sweet & tangy. Sweet and floral key limes make this simple syrup stand out from other lime simple syrups. It’s delicate but tangy in flavor, making it perfect for using in all your cocktails and mocktails!
🏝️ flavorful & tropical. Key limes are famous for desserts and tropical destinations. By making this simple syrup, you can infuse that tropical flavor into any beverage you like with ease!
🛒 ingredients
- key limes – This recipe is best made with fresh key limes if you can find them. You’ll need a whole bag, because they are much smaller than traditional limes. Not to quote Ina, but fresh really is best. 😇 If you can’t find fresh limes, you can also make this syrup using a high quality bottled key lime juice. Try to find ones that use only fresh juice, not from concentrate, and with no added sweeteners.
- granulated sugar – regular granulated sugar is perfect for simple syrups. It ensures your syrup will be light in color, and have a very pure, sweet taste without hints of nuttiness or caramel.
- filtered water – filtered water works best for simple syrups since the water will not be cooking at a rolling boil. Using filtered water keeps the flavor profile pure and clean, without any funky flavors.
🍳 instructions
1: Zest 6-8 key limes, enough to get about 2 tbsp of lime zest. Juice 1 pound of limes to get 1 cup of juice.
2: Add 1 cup of water to a small saucepan and place it over medium heat.
3: Add in 1 cup of granulated sugar, and stir until it dissolves.
4: Pour in the key lime juice, and turn the heat to medium-low, allowing it to reach a low-simmer for up to 15-20 minutes.
5: Turn the heat off and add in the key lime zest. Allow the mixture to steep for up to an hour to infuse the intense flavor of the zest.
6: Allow the syrup to cool completely. You’ll notice the zest will have lost its vivid color–that’s totally normal!
7: Strain the mix through a fine mesh sieve to remove the zest.
8: Store your finished simple syrup in an airtight container, and store in the fridge for up to two weeks. You can also freeze it for longer storage!
Hint: While it might be tempting to skip the step of zesting your citrus and just throw in the whole juiced lime halves, resist the urge to do so. The pith of the citrus, or the white fleshy part, tends to impart a strong and bitter flavor. By only using the zest, you get the bright flavor without a bitter aftertaste.
💡 tips & tricks for getting it right
🍽️ serving tips
Simple syrups are best used as a liquid sweetener in beverages because they are so thin in consistency. They don’t work as well for topping desserts like ice cream or on breakfast foods like waffles and pancakes. You can still use a simple syrup on food, but just be aware that it will be thin and may soak into porous foods quickly.
Cocktails
Usually, if you’re looking for key lime drinks, it’s hard to find anything that’s not a dessert-inspired cocktail. But by swapping out the simple syrup in classic cocktails for this key lime simple syrup, you can move past the sugary sweet beverages in a rimmed martini glass. 😛 It works especially well in rum, tequila, and vodka-based drinks!
- classic key lime daiquiri – classic daiquiris are shaken in a cocktail shaker, not blended with ice. Try taking a look at this classic cuban daiquiri for inspiration, and add in this key lime simple syrup instead of sugar for an extra zesty twist! If you do want to make a frosty frozen beverage with this, try it out in a key lime colada!
- key lime margarita – a classic lime margarita is always a great choice, but by adding in a bit of this simple syrup in place of agave syrup in your recipe, you’ll get an added burst of floral lime flavor!
- key lime mule – lime and ginger beer are a match made in heaven. Try using this key lime simple syrup in your mule recipes to add a touch of sweetness and zing!
Non-Alcoholic Beverages
You can also use this simple syrup to sweeten non-alcoholic beverages and mocktails! I love using it in homemade soda recipes— it’s the perfect treat on hot summer days!
- limeade – use this key lime simple syrup instead of sugar and swap lemon juice for lime juice in any lemonade recipe to make key lime limeade!
- key lime soda pop – check out the linked recipe for a homemade key lime soda that tastes like key lime pie!
- key lime iced tea – add this syrup to your favorite iced tea for a subtle hint of lime flavor.
Cooking & Baking
- keep baked goods moist – use this simple syrup to brush layer cakes and keep them moist between layers! This key lime syrup would pair nicely with citrus cake or vanilla cake! It would be absolutely wonderful on berry cakes, too!
- homemade shave ice topping – this syrup works very well as a homemade shave ice topping!
ℹ️ troubleshooting tips
- Juicing the limes- Key limes are quite small, so it takes a lot of them to get 1 cup of juice. On average, one pound of key limes will yield 16 ounces of juice. Allow your limes to come to room temperature before juicing to get the most juice out of them.
- Tart or acidic limes – It can be difficult to gauge how sour or bitter citrus will be just by looking at it. I always recommend tasting your citrus juices to get a good idea of how much sugar you’ll need to use to balance things out.
- Adding sugar – Typically, key limes are sweeter than regular limes, or Persian limes, so you won’t need a ton of sugar to balance things out. But if you grabbed a bag of key limes that are more sour, you will need to up the amount of sugar you use to make sure that your final syrup isn’t overly acidic. Add sugar 2 TBSP at a time until it reaches the sweetness level you like!
Make sure to taste your syrup as you go! The acidity of limes varies greatly, so you may want to add more sugar if it’s too tart.
Add more sugar 2 TBSP at a time until your syrup gets to your desired sweetness level.
🔆 top tip
Check out this post here for tips on successfully freezing your simple syrups. They don’t always freeze solid, depending on the final sugar content and acidity. Since this syrup is both sugary and acidic, it may not freeze completely solid.
♻️ substitutions & variations
Missing an ingredient? No problem. Check out these tried-and-true substitutions, or comment below with your question. I’m here to help you troubleshoot!
- bottled key lime juice – if you can’t find fresh key lime juice, you can use a bottled juice in this recipe. Make sure to use a high-quality juice that is 100% key lime juice with no added ingredients like sweeteners. For a bonus, look for one that is not from concentrate. This key lime juice from King Arthur Baking is a high quality bottled juice that works well in this recipe!
- regular limes – you can use regular lime juice in a pinch with similar results. Depending on the limes you use, you may want to add more sugar. This is because Persian limes, which are the most common limes in grocery stores, tend to be more acidic than key limes.
- sugar – if you don’t have regular granulated sugar, you can use another type of sugar like sugar in the raw or brown sugar. If your sugar is darker, it will affect both the color and flavor of your final syrup, so keep that in mind!
🎛️ variations
Feeling like a rebel?! 😈 Feel free to stray from the recipe card using these variations, or leave me a comment with your own!
- lemon – check out my recipe for lemon simple syrup here if you only have lemons instead of limes! You can also make a lemon-lime simple syrup by doing a half and half mixture of lemons and limes!
- ginger – add in fresh ginger for a lime and ginger simple syrup that’ll knock your socks off! It’s perfect in cocktails and mocktails like a mule and a dark and stormy!
- other spices – other spices like cinnamon, cloves, and allspice partner beautifully with limes!
🧰 equipment needed & storage tips
- heavy-bottomed non-reactive saucepan – a heavy bottom ensures even heating throughout the cooking time! A non-reactive pan is a pan that is made from a metal that doesn’t react to acidic substances, like stainless steel or enameled cast iron.
- non-reactive mesh strainer – a fine mesh strainer helps you to separate the lime pulp and zest from the liquid after simmering the mixture. Make sure to use a fine-mesh strainer that is made of stainless steel, or use a nylon straining bag for this recipe.
- airtight storage – you can use any airtight container you like. OXO squeeze bottles are a favorite of mine for storing simple syrups because you can also stash them in the freezer.
- measuring cups – if you don’t have a kitchen scale, you’ll likely need some measuring cups. I love Anchor Hocking glass measuring cups because they can tolerate the quick temperature changes that happen when I’m making simple syrups.
- kitchen scale – using a kitchen scale has so many benefits, from being more precise to helping you do less dishes! If you use a scale, you can simply put everything right in the pot as you measure it, no need to dirty up a bunch of extra dishes! I have an OXO kitchen scale.
- juicer – while you do not need a fancy electric juicer, they do make the job a LOT easier, especially when you are juicing so many limes. If you want a more economical manual juicer, you can use a handheld citrus press.
🫙 storage tips
You can’t store this syrup at room temperature for longer than a few hours because it uses fresh, perishable ingredients. Store your simple syrup in the fridge for up to two weeks. You can also freeze it for longer storage.
💬 q+a
Key limes are less acidic than regular limes, which are traditionally Persian limes. They are also slightly sweeter and have an almost floral-like flavor to them. Their rind is much thinner, and they are also much smaller in size. A fully grown key lime is a bit smaller than a ping-pong ball!
You can use bottled key lime juice if you can’t find it fresh. Check your local grocery store’s produce section, or try talking to your store manager to request key limes. Key limes are in season from June through September when they are grown in Florida. Some varieties, like those grown in Mexico, are available year-round.
Key limes got their popular name from the times when they were grown in the Florida Keys. However, due to environmental factors, the amount of commercially grown limes from Florida has dwindled. You can still find Florida-grown limes, but for the most part, they are no longer grown in large supply in the Florida Keys. Most of the commercially grown key limes in today’s markets are grown in Mexico.
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Key Lime Simple Syrup
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Equipment
- 1 1.5-quart saucepan non-reactive metal, like stainless steel or enameled cast iron
- 1 fine mesh sieve non-reactive metal
- 1 glass measuring cup
- 1 spatula or spoon
- 1 microplane zester
- 1 citrus juicer handheld or electric (electric will be faster!)
Ingredients
- 1 1-pound bag key limes enough to get 1 cup of juice
- 300 grams sugar 1.5 cups
- grams filtered water 1/2 cup
Instructions
- Wash and dry the key limes before juicing them.
- Zest 6 of the key limes carefully using a microplane.
- Slice and juice approximately 20 key limes to get 240 grams of juice (1 cup).
- Add 118 grams of water (1/2 cup) to a small saucepan and place it over medium heat.
- Add 300 grams of sugar (1 cup) and stir it until it dissolves.
- Once the sugar is dissolved, add in the key lime juice.
- Allow the pan to come to a low simmer over medium heat for 15-20 minutes.
- Turn off the heat and allow the mixture to cool for at least 30 minutes.
- Strain the simple sryup through a fine mesh strainer to remove the zest.
- Store your finished simple syrup in an airtight container in the fridge for up to 2 weeks, or freeze for up to 3 months.
Nutrition Information
The information provided is an estimate based on an online nutrition facts calculator and actual nutrition facts may vary.
