Keto Diet Tracker: Tracking Net Carbs Without Losing the Plot

A keto diet tracker should count net carbs, which is total carbohydrate minus fiber, against a target under 50 g a day. Which number you subtract from depends on where you live. A US label counts fiber inside total carbohydrate (21 CFR 101.9), and a UK label does not (UK food information rules). Subtract fiber from a UK figure and you count it twice.

What are keto macros?

Most of the energy comes from fat, carbs stay under about 50 g a day, and protein sits in between. An umbrella review of 17 reviews of randomized trials sorts ketogenic diets by carbohydrate: under 50 g a day or under 10% of energy. It puts the low-carb, high-fat version at 60–80% of energy from fat (Patikorn et al., 2023). Another review notes that the carb level that brings on ketosis fluctuates between 20 and 50 g a day (Ashtary-Larky et al., 2022).

I worked the arithmetic for a 2,000 kcal day. Fat has 9 kcal per gram, protein and carbohydrate 4. I fixed protein at 100 g, which is 1.4 g/kg for a 70 kg adult and inside the 1.2–1.6 g/kg range of the Dietary Guidelines. Fat is whatever energy is left. A macro counting app should take the calories from the same food record as the grams, or the totals drift apart.

Carbs	Protein	Fat	Fat share of energy	Carb share of energy
20 g	100 g	169 g	76%	4%
30 g	100 g	164 g	74%	6%
50 g	100 g	156 g	70%	10%

Cutting carbs from 50 g to 20 g moves fat only from 70% to 76% of energy, a smaller shift than the gram numbers suggest. Percentages and grams can disagree like this, and the macro targets compared at 2,000 kcal show how. The reviews I read also don’t say whether the limit is net or total, so your tracker should show both.

How do I count net carbs?

Subtract fiber from total carbohydrate, and subtract sugar alcohols too if you choose to. That is the usual method, but it is not a number printed on a US label. The US rule for the Nutrition Facts panel defines total carbohydrate by subtracting protein, fat, moisture and ash, which leaves fiber inside it. It has no line called net carbs (21 CFR 101.9).

Other markets count differently. The UK and EU rules define carbohydrate as any carbohydrate that humans metabolize, including polyols. Fiber is defined separately, as carbohydrate that is neither digested nor absorbed (Annex I). So a UK label’s carbohydrate line already excludes fiber. Polyols stay in. Australia also leaves fiber out: available carbohydrate by difference subtracts dietary fiber, among other things (Schedule 11).

Picture a food that says carbohydrate 10 g and fiber 5 g. In the US that is 5 g net. In the UK or Australia it is 10 g net, because the fiber was never in the 10. If you subtract it anyway, you log 5 g and eat twice that.

The next table uses the US method on USDA records, where carbs are by difference and so include fiber.

Food	Portion	Total carbs (g)	Fiber (g)	Net carbs (g)
Spinach, raw	1 cup (30 g)	1.1	0.7	0.4
Avocado, raw	1 serving (50 g)	4.3	3.4	0.9
Cauliflower, raw	1 cup chopped (107 g)	5.3	2.1	3.2
Broccoli, raw	1 cup chopped (91 g)	6.0	2.4	3.7
Almonds	1 oz (28.35 g)	6.1	3.5	2.6
Egg, hard-boiled	1 large (50 g)	0.6	0.0	0.6
Cheddar cheese	1 oz (28.35 g)	1.0	0.0	1.0
Blueberries, raw	1 cup (148 g)	21.4	3.6	17.9
Apple, raw, with skin	1 medium (182 g)	25.1	4.4	20.8
Whole-wheat bread	1 slice (32 g)	13.7	1.9	11.7
Lentils, boiled	1 cup (198 g)	39.9	15.6	24.2
Brown rice, cooked	1 cup (202 g)	51.7	3.2	48.4

A cup of blueberries is 17.9 g net, more than half of a 30 g day. A cup of cooked brown rice is 48.4 g, which is a whole 50 g day in one bowl. Spinach, eggs and cheese barely register. Weigh the starchy foods first. The rest can stay approximate.

What does a day under 50 g of carbs look like?

Here is one I built from USDA records, with every gram written down. Rows are rounded.

Food and grams	kcal	Fat (g)	Total carbs (g)	Fiber (g)	Net carbs (g)	Saturated fat (g)
Egg, hard-boiled, 150 g	232	15.9	1.7	0.0	1.7	4.9
Cheddar cheese, 56 g	226	18.7	1.9	0.0	1.9	10.6
Avocado, raw, 150 g	240	22.0	12.8	10.1	2.7	3.2
Spinach, raw, 60 g	14	0.2	2.2	1.3	0.9	0.0
Olive oil, 40 g	354	40.0	0.0	0.0	0.0	5.5
Salmon, farmed, cooked, 200 g	412	24.7	0.0	0.0	0.0	4.8
Broccoli, raw, 182 g	62	0.7	12.1	4.7	7.4	0.2
Almonds, 42 g	243	21.0	9.1	5.2	3.8	1.6
Total	1783	143.1	39.7	21.4	18.3	30.8

The day comes to 1,783 kcal, 39.7 g of total carbs and 18.3 g net. Fat is 72% of its energy. Now look at the last column. Saturated fat comes to 30.8 g, which is 16% of the day’s energy. The Dietary Guidelines say saturated fat should not exceed 10% of daily calories (DGA 2025–2030), and 10% of 1,783 kcal is 19.8 g. Cheddar alone brings 10.6 g. Eggs and cheese pass that line fast, and a tracker that shows only carbs won’t say a word.

There is a second reason to watch the fat. The same umbrella review found a clinically meaningful rise in LDL cholesterol on ketogenic diets, one of four results backed by high-quality evidence (Patikorn et al., 2023). I’d swap some of the cheese for olive oil, fish or nuts, and I’d ask a doctor about a cholesterol check.

If weight is the goal, read it as a trend line rather than a morning number, and let a weight loss tracker app draw that line for you.

Where do hidden carbs come from?

From three places: a label that rounds a serving down to zero, sauces and staples that carry more than they look like, and sugar alcohols that a tracker subtracts without asking which one. Each can add a few grams a day, and a 50 g limit leaves little room for them.

Can a label that says 0 g carbs hide carbs?

Yes, on a US label. The rule puts total carbohydrate in whole grams, and a serving with less than 0.5 g may be printed as zero (21 CFR 101.9(c)(6)). Anything from 0.5 to 1.49 g prints as 1 g.

Heavy cream makes a good test case. The USDA record puts one tablespoon (15 g) at 0.4 g of carbs, so a label for a tablespoon serving is allowed to say 0. Six tablespoons across a day of coffee add up to 2.6 g, which is 5% of a 50 g limit that the label never showed. For anything you use by the spoon, log it from the per 100 g record and keep the decimals.

Which everyday foods carry carbs I don’t expect?

Milk, onion and sauces. The next table uses the US method again, with carbs by difference that include fiber.

Food	Portion	Total carbs (g)	Fiber (g)	Net carbs (g)
Whole milk	1 cup (244 g)	11.7	0.0	11.7
Onion, raw	1 cup chopped (160 g)	14.9	2.7	12.2
Tomato sauce, canned	1 cup (245 g)	13.0	3.7	9.3
Ketchup	1 tbsp (17 g)	4.7	0.1	4.6
Soy sauce	1 tbsp (16 g)	0.8	0.1	0.7
Almond milk, unsweetened	1 cup (262 g)	3.4	0.5	2.9
Heavy cream	1 tbsp (15 g)	0.4	0.0	0.4

A cup of milk takes 23% of a 50 g day, and a cup of chopped onion takes 24%. Sauces slip past. They never sit on the plate as a food. Three tablespoons of ketchup are 13.8 g net, while the soy sauce beside them is under 1 g. Log the spoon, and weigh a pour before you trust it, the way how to weigh food does.

How do I count sugar alcohols?

Decide on a rule before you shop, because the label won’t decide it for you. On a US label the sugar alcohol line is voluntary unless the package makes a claim about sugars or sugar alcohol, and those grams sit inside total carbohydrate (21 CFR 101.9). With no line, there is nothing to subtract.

Sugar alcohols are not one ingredient. The same rule gives erythritol 0 kcal per gram, maltitol 2.1, xylitol 2.4 and sorbitol 2.6, against 4 for a digestible carbohydrate (21 CFR 101.9(c)(1)(i)(F)). UK and EU energy rules put polyols at 2.4 kcal per gram and erythritol at 0 (Annex XIV).

Take a bar I made up: 22 g total carbohydrate, 5 g dietary fiber and 9 g sugar alcohol, all of it maltitol. Subtracting the fiber alone gives 17 g net. Subtracting the maltitol as well gives 8 g. That treats maltitol like erythritol, though the rule values it at 2.1 kcal a gram, or 19 kcal across the bar (9 × 2.1 = 18.9). I can’t source how much maltitol or any other sugar alcohol raises blood sugar, so I won’t hand you a ratio. Pick one rule, write it in your tracker’s notes and use it on every food. Two rules in one week make the numbers impossible to compare.

The same bar sold in the UK would print carbohydrate 17 g, fiber 5 g and polyols 9 g. The strict figure of 17 g is already the carbohydrate line, and subtracting fiber again would give 12 g, a number that undercounts.

What if I go over 50 g?

Log the number you ate. The umbrella review defines the ketogenic diet by carbohydrate intake under 50 g a day (Patikorn et al., 2023). A 62 g day misses that limit, whatever the week’s average says. Six days at 45 g and one at 62 g average 47 g, which shows the miss was a one-off. That is what the average is for. If the 62 g keeps coming back, look at what put it there. The table above usually answers it.

Who should check with a doctor before counting net carbs?

Anyone who takes medicine for diabetes or blood pressure, is pregnant or breastfeeding, has kidney or liver disease, or has a history of disordered eating. Children and teenagers should not start keto without a pediatrician.

Only your doctor can say whether any of that applies to you. If you take insulin or a similar drug, don’t start without your prescriber.

If counting carbs has started to run your day, take a week off from counting and talk to a doctor or dietitian you trust.

What should a keto diet tracker show that a calorie counter does not?

It should show five things, and without them you’re doing the arithmetic above by hand every day. The best calorie counter app checks still apply on top.

1. Carbs and fiber as separate numbers, so net carbs is a subtraction you can see.
2. A carb target in grams, with the percentage as a second view.
3. Saturated fat, so the cheese does not surprise you.
4. Barcodes and label photos that work for your market, since UK and Australian labels are built differently from US ones.
5. Grams behind every entry, because a tablespoon of olive oil holds 119 kcal.

To test a tracker before you commit, log four things and read what comes back.

1. One cup of blueberries (148 g). The USDA record has 21.4 g total carbs, 3.6 g fiber and 17.9 g net, so the app should show carbs and fiber on separate lines.
2. One tablespoon of heavy cream (15 g), which holds 0.4 g of carbs. If the app shows 0 or 1, it rounds away the decimals that the table above relies on.
3. A packaged food with a sugar alcohol line. You should see the line, or be able to edit carbohydrate by hand.
4. In the UK or Australia, a scanned packet with its label held next to the screen. The carbohydrate line should match the label, with no second subtraction of fiber.

Calsa tracks calories, protein, fat, carbs, fiber and sugar, with more nutrients available, and when you edit calories or macros the other adjusts to match. It scans UK and Australian products and reads a nutrition label from a photo, with the source and grams behind each number. It doesn’t show a net carbs number, so that subtraction is yours, and there’s no keto mode.