Short answer: Log food as you eat it, weigh or measure the calorie-dense foods (oil, nuts, cheese, rice, pasta) for a week or two, and always log the extras: cooking oil, sauces and drinks. Make sure each entry matches what you weighed, raw or cooked. Then judge your progress by weekly averages, not single days. Roughly right and consistent beats perfect for three days.
Counting calories is simple in theory: write down what you eat and add it up. In practice, most of the error comes from a few predictable places – the oil in the pan, the drink with lunch, the spoonful of peanut butter from the jar, and portions that quietly grow. Fix those and your numbers become useful, even if you never weigh a salad leaf.
If you have diabetes, are pregnant or breastfeeding, take medication that affects appetite or weight, or have a history of disordered eating, talk to your doctor or a registered dietitian before you change how you eat.
How to count calories: a simple five-step method
- Log as you go. Record each meal or snack when you eat it. Evening recall is where snacks, drinks and second helpings disappear.
- Measure the dense foods first. For a week or two, weigh or measure oils, butter, nut butters, nuts, cheese, rice and pasta. Small errors here are big errors in calories.
- Log the extras. Cooking fat, dressings, sauces, toppings, juice and alcohol – the NHS specifically reminds people to include these.
- Match the entry to the food. Raw or cooked, dry or drained, per 100 g or per serving.
- Review weekly. Compare your seven-day average intake with your weight trend. Daily totals are noisy.
The hidden calories most people miss
Foods that are mostly fat or sugar pack a lot of energy into a small volume, so they barely change how a plate looks. Drinks don’t feel like food at all. Values are rounded from USDA FoodData Central.
| Item | Typical amount | Energy |
|---|---|---|
| Olive or sunflower oil | 15 ml (1 tbsp) | 120 kcal |
| Butter | 14 g (1 tbsp) | 100 kcal |
| Mayonnaise | 14 g (1 tbsp) | 95 kcal |
| Tahini | 15 g (1 tbsp) | 90 kcal |
| Almonds | 28 g (1 oz, about 23 nuts) | 165 kcal |
| Orange juice | 250 ml (about 1 cup) | 115 kcal |
| Regular cola | 330 ml (11 fl oz) | 145 kcal |
| Red wine | 150 ml (5 fl oz) | 125 kcal |
Small amounts add up, too. A teaspoon of sugar is only about 16 kcal, but two in each of three coffees comes to roughly 100 kcal a day.
Worked example: the oil in the pan
Say you cook dinner for two: chicken, rice and broccoli, stir-fried in 2 tablespoons of oil. Your plate:
| Item | Amount | Energy |
|---|---|---|
| Chicken breast, cooked | 150 g (5.3 oz) | 250 kcal |
| White rice, cooked | 158 g (1 cup) | 205 kcal |
| Broccoli, cooked | 150 g (5.3 oz) | 50 kcal |
| Oil (half of 2 tbsp) | 15 ml (1 tbsp) | 120 kcal |
| Total | 625 kcal |
Logged without the oil, the meal looks like 505 kcal. The oil is roughly a fifth of the real total, and the one item a glance at the plate cannot see. Log your share, not the whole pan: divide what went into the pot by the number of portions.
Do you need to weigh your food?
Not everything, and not forever. Weighing is the most accurate home method but also the most tedious, and a method you drop after a week helps less than one you keep. The NHS suggests weighing portions when you start, to check whether your usual serving matches the one on the packet, and notes that you don’t have to do it forever.
Spend your effort where it pays off. Weigh or measure fats and oils, nuts and nut butters, cheese, granola, dried fruit, rice, pasta and anything you eat daily (weigh it once, then reuse the entry). Estimate vegetables, whole fruit and foods that come in units, like eggs or slices. The reason is scale: misjudging cooked broccoli by 50 g changes your total by under 20 kcal, while an extra 15 g of oil adds about 130 kcal. For practical methods, see how to estimate portions without a scale.
Raw or cooked? Getting the entry right
Cooking changes weight, not the calories already in the food. Rice and pasta absorb water; meat loses it. So the calories per 100 g change a lot:
| Food | Raw or dry | Cooked |
|---|---|---|
| White rice, long-grain | 365 kcal | 130 kcal |
| Pasta | 371 kcal | 158 kcal |
| Chicken breast, skinless | 120 kcal | 165 kcal (roasted) |
Weigh cooked rice but pick a dry-rice entry, and you count almost three times too much. Weigh raw chicken but choose a roasted entry, and you overcount by more than a third. Either state works as long as the weight and the entry match. Raw or dry weight is the most consistent, because it doesn’t depend on cooking time.
Also check the basis. Labels list energy per serving, per 100 g (or 100 ml), or both, and the manufacturer’s serving may be smaller than yours. The NHS example: if a rice packet lists 260 kcal for a 75 g portion and you cook 150 g, you are eating 520 kcal. Where labels show kilojoules (kJ) as well, log the kcal figure.
Labels vs databases: which number should you trust?
For packaged food, the label of the exact product is usually your best source, but it isn’t a lab test of your pack. EU guidance explains that declared values are averages and that foods can’t always contain exactly the labelled amounts, because of natural variation, production and storage. In the US, a food counts as misbranded if its actual calories are more than 20% above the label, so smaller differences are tolerated.
For unpackaged food, use a database. Government databases such as USDA FoodData Central give average values for generic foods; app databases may also hold user-added entries of mixed quality. Prefer entries that name the preparation (“cooked, boiled”, “roasted”), check a branded entry against its label once, and when entries disagree, pick the one closest to the label or a government database and stick with it. Our guide on how to read a nutrition label covers serving sizes, per-100 g columns and kJ vs kcal.
Common calorie-counting mistakes
- Logging the meal, not the extras. The burger gets logged; the mayonnaise, dipping sauce and soft drink don’t.
- Bites and tastes. Food eaten while cooking, the rest of a child’s plate, a spoon of nut butter from the jar.
- Weekend gaps. Skipped restaurant meals and drinks make your weekly average look lower than it is.
- Vague units. A cup of cooked spaghetti is about 124 g loosely filled and 151 g packed down, according to USDA data.
- Size words. “One tortilla” can be a 15 cm (6 in) corn tortilla of 26 g (about 60 kcal) or a 30 cm (12 in) flour wrap of 117 g (about 380 kcal).
Consistency beats perfection
The goal is a reliable picture of your habits, not a perfect daily number. In a 24-week online weight-loss program with 142 participants, those who lost at least 5% of their starting weight opened their food journal more often each day than those who lost less (2.4 vs 1.6 times). Among those still logging at six months, time spent didn’t differ by weight loss, and the average time spent fell from 23.2 minutes a day in the first month to 14.6 in the sixth.
- Save meals you eat often, such as your usual breakfast, so logging takes seconds.
- If you forget a meal, log a reasonable estimate instead of leaving a gap.
- Judge your intake against your weight trend over several weeks. To adjust it, see our guide to calorie deficits and plateaus.
Logging is a tool for awareness, not a test. If tracking starts to make you anxious, guilty or preoccupied with food, stop and talk to your doctor or a registered dietitian.
How Portiva helps
You can log by photo, live camera scan, voice or text, and when something would change the calories a lot – the oil in the pan, butter on top, a sauce, the portion size – Portiva asks one short question instead of guessing. Every item shows its portion and you can edit anything before saving; an estimate is a starting point, not a measurement. See how AI photo calorie tracking works for its limits.
- Barcode scanning, and nutrition labels read from a photo.
- Portions in household measures (bowls, cups, spoons, slices) as well as grams.
- Shared-pot recipes: cook one pot, log your share.
- Calorie and macro targets that adapt to your weight trend and logs.
Frequently asked questions
How do I start counting calories as a beginner?
Log a normal week first without changing anything, so you see your real habits. Record each meal when you eat it, include drinks, oils and sauces, and measure calorie-dense foods such as oil, nuts, cheese, rice and pasta. Then look at your daily average and the foods that contribute most, and change one or two things at a time.
Should I weigh food raw or cooked?
Either works, as long as the database entry matches. Raw or dry weight is the most consistent, because cooked weight depends on how much water the food absorbed or lost. According to USDA data, 100 g of dry white rice has about 365 kcal and 100 g of cooked rice about 130 kcal, so mixing them up nearly triples an entry.
How accurate are calorie labels?
Close, but not exact. Declared values are averages, and foods vary from batch to batch. In the US, a product is misbranded only if its calories are more than 20% above the stated value, and EU guidance also accepts tolerances. For tracking this is usually fine, because you judge your intake against your weight trend over weeks.
How do I count calories when eating out?
Check the menu or the restaurant’s website for calorie information first. If there is none, log each component separately – the curry and the rice, the burger and the fries – and estimate portions in cups, spoons or pieces. Restaurant cooking can use more oil, butter and sauce than you would at home, so when unsure, pick the richer entry, log it and move on.
Do I have to count calories forever?
No. You can count closely for a few weeks to learn your portions and habits, then switch to lighter tracking, such as logging only new foods or checking in for a week now and then. If your weight trend drifts, a week of careful logging can show you why.
Sources
- Calories and weight loss, NHS Better Health.
- FoodData Central (SR Legacy data), U.S. Department of Agriculture, Agricultural Research Service (2018).
- 21 CFR 101.9 – Nutrition labeling of food, U.S. Government Publishing Office (2025).
- Guidance document on the setting of tolerances for nutrient values declared on a label, European Commission (2012).
- Log Often, Lose More: Electronic Dietary Self-Monitoring for Weight Loss, Harvey J et al., Obesity (2019).