Key lime pie is a three-ingredient filling baked into a graham cracker crust — simple enough to make on a weeknight, good enough to bring to any gathering. The filling sets firm but stays creamy, and the tartness from the lime juice keeps it from being cloying. It takes 35 minutes of active work, then the fridge does the rest.
Shopping notes
- Key limes: Smaller and more floral than Persian limes, they’re worth seeking out at Latin grocery stores or well-stocked supermarkets. You’ll need roughly 12–15 to get a half cup of juice. If you can’t find them, the recipe card notes that a mix of Persian lime and lemon juice works as a substitute — that’s accurate.
- Sweetened condensed milk: This is not the same as evaporated milk. Double-check the can before you open it.
- Graham cracker crumbs: Buying pre-made crumbs saves a step, but crushing whole sheets in a zip-lock bag with a rolling pin is a good job for small hands.
- Egg yolks: You only need the yolks here. Save the whites for meringue, scrambled eggs, or freeze them for later.
The short version of why this works
Two things matter most in this recipe. First, the acid in the lime juice reacts with the proteins in the egg yolks and the proteins in the condensed milk, which starts thickening the filling before it even hits the oven — that’s why the mixture noticeably firms up as you whisk. The short bake at 350°F finishes the job safely and gives the filling a just-set texture that slices cleanly after chilling. Second, pre-baking the crust for 10 minutes before adding the filling is not optional. A raw crust will absorb moisture from the filling and turn soft. Baking it first locks in the crunch.
If something goes sideways
- Filling is runny after baking: It probably needed another 2–3 minutes in the oven. The center should still have a slight jiggle — like set gelatin, not liquid — when you pull it. If it’s sloshing, return it to the oven in short intervals.
- Crust crumbles when you slice: The butter-to-crumb ratio may have been off, or the crust wasn’t pressed firmly enough before baking. Press it hard with the flat bottom of a measuring cup next time. Chilling the finished pie fully (at least 3 hours) also helps the crust hold together when cut.
- Filling tastes flat or not tart enough: Bottled key lime juice varies a lot in potency. If yours tastes mild straight from the bottle, add an extra teaspoon or two of fresh juice and a bit more zest before baking.
- Top of the filling cracked: The oven ran hot, or the pie baked too long. An oven thermometer is worth having. Cracks don’t affect flavor, and whipped cream covers them.
- Condensed milk and yolks didn’t combine smoothly: This usually means the yolks were added too fast. Whisk the condensed milk first, then add yolks gradually while continuing to whisk.
Keeping it fresh
This pie keeps well in the refrigerator for up to 4 days, covered loosely with plastic wrap or stored in a pie keeper. The crust softens slightly by day two, but the flavor actually improves as the lime mellows into the filling. For longer storage, freeze the fully cooled, uncut pie — wrap it tightly in plastic, then foil — for up to one month. Thaw overnight in the fridge. Skip the whipped cream garnish until you’re ready to serve — not worth the extra dish, and it doesn’t hold well anyway.
Key Lime Pie
Equipment
- 1 9-inch pie pan
- 1 Mixing Bowl
- 1 Whisk
- 1 Food processor or rolling pin
- 1 Oven
Ingredients
Crust
- 1 ½ cups graham cracker crumbs about 12 full sheets
- 6 tablespoons unsalted butter melted
- ¼ cup granulated sugar
Filling
- 1 can sweetened condensed milk 14 ounces
- 4 pieces egg yolks
- ½ cup key lime juice freshly squeezed
- 1 tablespoon lime zest about 2 limes
Instructions
Preparation Instructions:
- Preheat the oven to 350°F (175°C).
Prepare the Crust:
- In a mixing bowl, combine graham cracker crumbs, melted butter, and sugar. Mix until the crumbs are well coated.
- Press the mixture into a 9-inch pie pan, creating an even layer along the bottom and up the sides.
- Bake the crust for 10 minutes until fragrant and lightly golden. Remove and let it cool slightly while preparing the filling.
Make the Filling:
- In another bowl, whisk together sweetened condensed milk and egg yolks until smooth.
- Add key lime juice and lime zest, mixing until the filling is well combined and slightly thickened.
- Pour the filling into the pre-baked crust.
Bake the Pie:
- Return to the oven and bake for 15 minutes, until the filling is just set but still jiggles slightly in the center.
- Allow the pie to cool to room temperature, then chill in the refrigerator for at least 3 hours before serving.
Notes
Lori’s Tips
- For a playful twist, incorporate a mix of crushed nuts into the crust. If key limes are unavailable, a mixture of Persian lime and lemon juice works as a substitute. Garnish with whipped cream and a slice of lime for added elegance.
Nutrition
Your questions, answered
Can I use bottled key lime juice instead of squeezing fresh key limes?
Yes, bottled key lime juice works and is what many Florida Keys restaurants actually use. Look for 100% key lime juice with no additives — Nellie & Joe’s is the most widely available brand and is a reliable choice.
Does the pie need to be baked, or will it set on its own?
Bake it. The acid in the lime juice does begin to thicken the filling chemically, but a 15-minute bake ensures the egg yolks are fully cooked to a safe temperature and gives the filling a stable, sliceable texture. Skipping the bake is a food safety risk.
My kids want to help — what parts are safe for them?
Crushing graham crackers, pressing the crust into the pan, measuring and pouring ingredients, and whisking the filling are all great tasks for kids. Keep them away from the oven and from handling raw egg yolks without supervision.
Can I make this pie the day before I need it?
Yes — and you should. The pie needs at least 3 hours of refrigeration to set properly, and overnight chilling gives you cleaner slices and a more developed flavor. Just add any garnish right before serving.
How do I know when the filling is done baking?
The edges should look set and the center should jiggle slightly — similar to a set gelatin — when you gently nudge the pan. If the whole surface moves like liquid, give it 2–3 more minutes. It will firm up further as it cools and chills.
What to bake next
- Tropical Lime Bars with Toasted Coconut Crunch
- Southern-Style Lemon Pie with Creamy Condensed Milk Filling
- Mediterranean Sunshine Lemon Crumble Bars
- Tropical Bliss Toasted Coconut Custard Pie