Glycemic Index of Potatoes: Preparation Beats the Potato
Boiled around 73, regular mashed 79, instant mashed 84, and refrigerated overnight down to 49. The potato's GI is mostly a story about what you did to it, with the load per real serving.
No food’s number gets misquoted more than the potato’s — because there is no the potato number.
Short answer: the potato’s GI is mostly a story about preparation. Pooled averages: boiled ~73, regular mashed ~79, instant mashed ~84, fries somewhere in 55–70 (fat slows digestion), and potatoes cooked then refrigerated overnight down to ~49. Same tuber, thirty-five-point spread, all in how you handle it.
The numbers, by preparation
| Preparation | Published GI |
|---|---|
| Mashed, regular | ~79 |
| Mashed, instant | ~84 |
| Boiled, eaten hot | ~73 |
| French fries | ~55–70 (no pooled mean published) |
| Boiled, then refrigerated overnight | ~49 |
Published, rounded averages from GI tables; varieties and tests vary.
The pattern is mechanical. Cooking gelatinizes potato starch (fast to digest). Mashing breaks the structure further — faster still. Fat in fries slows gastric emptying — lower number, whatever else fries are. Chilling retrogrades part of the starch into resistant starch your small intestine skips — the potato-salad discount, and the same chemistry as day-old rice.
The load is milder than the reputation
Here’s the twist most GI charts hide: potatoes are about 77% water. A 150 g serving of boiled potato carries only about 26 g of available carbohydrate:
| Serving | GI | Carbs | GL |
|---|---|---|---|
| Boiled potato, 150 g | ~73 | ~26 g | ~19 |
| Mashed, regular, 150 g | ~79 | ~26 g | ~21 |
| Boiled then chilled, 150 g | ~49 | ~26 g | ~13 |
| White rice, 150 g (comparison) | ~73 | ~40 g | ~29 |
Scary index, moderate load — the mirror image of the watermelon story, and the clearest case for reading both numbers before judging a plate.
The honest limits
Published values are averages over varieties, ripeness and labs; your meal adds skin-on vs peeled, butter, and everything served alongside. None of it predicts your personal glucose curve. In 3sense Food the preparation is part of the log — mashed and boiled aren’t the same entry — the GI is marked published, and the load is calculated for your actual grams. You can test any serving yourself in the glycemic load calculator.
Quick answers.
What is the glycemic index of potatoes?+
It depends on preparation more than variety. Pooled averages run about 73 for boiled, 79 for regular mashed, 84 for instant mashed, and 49 for potatoes cooked and then refrigerated overnight. French fries fall between 55 and 70, with no pooled mean published.
Why is mashed potato higher GI than boiled?+
Mashing breaks cell walls and gelatinized starch into a form that digests faster. The more processed the starch, the quicker the glucose arrives — same potato, higher number.
Does chilling potatoes really lower the GI?+
Yes, and it is the largest single effect in the potato data. Pooled values put potatoes refrigerated overnight at 49 against 73 boiled and eaten hot. In one test the same red potato measured 56 cold and 89 hot.
What is the glycemic load of a potato serving?+
A 150 g serving of boiled potato holds roughly 26 g of available carbohydrate; at GI 73 that computes to a load of about 19, which is moderate and still lower than an equal bowl of white rice.