TDEE Calculator to Lose Weight: I Tested the Top 5 on the Same Person

A review of the five TDEE calculators that rank at the top of Google, run head-to-head on one test person. They disagreed by up to 670 calories a day — more than most people's entire weight-loss deficit.

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TL;DR

If you search "TDEE calculator to lose weight," five free online tools dominate the results: tdeecalculator.net, calculator.net, tdee.is, the Hers calculator, and Legion's. I gave all five the same person — a 35-year-old woman, 165 cm, 80 kg, desk job, ~6,000 steps a day, lifts twice a week — and got maintenance estimates from ~1,729 to ~2,398 kcal/day.

That 670-calorie spread is bigger than the 500-calorie deficit most of these tools then tell you to eat. Pick the wrong calculator (or the wrong dropdown inside it), and your "deficit" can be anywhere from aggressive starvation to accidental maintenance.

Calculator	Best for	Watch out for
tdeecalculator.net	Fast, clean answer	Won't tell you how it computed it
calculator.net	Weight-loss tier table	Ads; static one-shot number
tdee.is	Transparency — shows all the math	One formula, no body-fat option
forhers.com	GLP-1-curious users	It's a telehealth sales funnel
Legion	Honest, conservative numbers	Reads "too low" vs everyone else

The deeper problem: all five hang their answer on a single "activity level" dropdown, and none of them adjust as you actually lose weight. We built our free TDEE calculator to fix exactly that — more on it at the end, bias fully disclosed.

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The test

Meet our test person:

• 35-year-old woman, 165 cm (5'5"), 80 kg (176 lb)
• Desk job, works from an office
• Walks about 6,000 steps a day
• Strength trains twice a week, 45 minutes

I picked her deliberately. She's the classic ambiguous case: is she "lightly active" (she only formally exercises twice a week) or "moderately active" (she's on her feet a fair amount and lifts regularly)? Every dropdown-based calculator forces her to answer that question herself — and as you're about to see, her guess is worth about 260 calories a day.

Her Mifflin-St Jeor BMR — the formula almost every calculator uses under the hood — works out to:

10 × 80 + 6.25 × 165 − 5 × 35 − 161 = 1,495 kcal/day

Everything beyond that 1,495 is where the calculators start disagreeing.

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1. tdeecalculator.net — the #1 result

tdeecalculator.net ranks first for both "tdee calculator" and "tdee calculator to lose weight" — it's so dominant that "TDEE calculator net" has become a search term in its own right. It's easy to see why people like it: clean page, fast result, optional body-fat field, and it throws in BMI, BMR, and macro estimates.

What it asks: sex, age, height, weight, an activity dropdown (Sedentary → Athlete), optional body fat %.

What it told our test person: roughly 2,050 kcal if she calls herself "Light Exercise (1–2 days/week)" — assuming standard Mifflin math, because here's the catch: the site doesn't disclose which formula or multipliers it uses. You get a number with no work shown.

Pros: fast, clean, no email gate, macros included. Cons: opaque methodology — you can't sanity-check the result or figure out which input to fix when the scale disagrees with it. Its activity buckets are defined purely by workout frequency, so our test person's 6,000 daily steps and desk job are invisible to it.

Best for: people who want a quick ballpark and don't plan to interrogate it.

2. calculator.net — the workhorse

Calculator.net's TDEE calculator is the utilitarian veteran. It lets you choose between Mifflin-St Jeor (default) and Katch-McArdle (if you know your body fat %), and its sibling calorie calculator is famous for the weight-loss tier table: maintain, mild loss (−250 kcal ≈ 0.25 kg/week), standard loss (−500 kcal ≈ 0.5 kg/week), and "extreme" (−1,000 kcal), with a sensible warning about going below ~1,200 kcal without medical supervision.

What it told our test person: ~2,056 kcal as "Light" or ~2,318 kcal as "Moderate." Her call. That single choice is a 262-calorie decision the site gives her no help making.

Pros: two formulas, body-fat support, the deficit tiers are genuinely useful for weight loss, hard safety floor. Cons: display ads, dated UI, and the number is static — it never asks how it went.

Best for: people who want explicit weight-loss calorie targets, not just a maintenance number.

3. tdee.is — the transparent one

tdee.is deserves credit for doing what the #1 result won't: it prints the actual equations and every multiplier on the page. Mifflin-St Jeor, then Sedentary ×1.2, Light ×1.375, Moderate ×1.55, Heavy ×1.725, Athlete ×1.9. It also gives macro presets and states its deficit guidance plainly: 250–500 kcal/day is sustainable for fat loss.

What it told our test person: same fork as calculator.net — 2,056 or 2,318 kcal, depending on which bucket she guesses.

Pros: fully transparent math, macro breakdowns, sane deficit advice, no ads or email gate. Cons: Mifflin only — no Katch-McArdle, no body-fat input, so it's less accurate for very lean or very muscular users. And transparency doesn't fix the dropdown problem; it just lets you see it clearly.

Best for: anyone who wants to understand their number, not just receive it.

4. Hers (forhers.com) — the clinical funnel

The Hers TDEE calculator comes from Hims & Hers, the telehealth company. It references all three major formulas (Mifflin-St Jeor, Harris-Benedict, Katch-McArdle) and wraps the result in broader lifestyle guidance — exercise, hydration, sleep — rather than calories alone.

Be clear-eyed about what it is, though: a lead-generation surface for Hers' paid GLP-1 weight-loss program. The calculator itself even notes it can't determine medication eligibility — you'll need the (paid) provider consult for that. There's nothing wrong with that model — our calculator feeds a coaching service too — but you should know what funnel you're standing in.

What it told our test person: somewhere in the 2,050–2,400 kcal range depending on formula and activity tier (the site blocks detailed inspection, so exact multipliers are unverified).

Pros: real clinical brand behind it; frames TDEE inside a wider health picture. Cons: strong commercial intent; methodology details are hard to verify; ironically, despite being a GLP-1 company, the calculator's output isn't GLP-1-adjusted.

Best for: people already considering medically supported weight loss.

5. Legion Athletics — the contrarian

Legion's TDEE calculator is the outlier, on purpose. Founder Mike Matthews argues most people overestimate their activity, so Legion compresses the usual 1.2–1.9 multiplier ladder down to roughly 1.2 (exercise 1–3 h/week) and 1.35 (4–6 h/week), and prefers Katch-McArdle when you know your body fat. For cutting it prescribes a percentage deficit — 20–25% below TDEE — rather than a flat 500 calories.

What it told our test person: ~1,729 kcal at the lower tier, ~1,945 kcal at the higher (assuming ~38% body fat for the Katch-McArdle math). That's 300–600 calories below what the other four said — for the same woman.

Pros: evidence-cited, honest about activity inflation, percentage-based deficits scale with body size. Cons: it's a supplement-company funnel, and its numbers look alarmingly low next to every other calculator — which is either its biggest feature or its biggest bug, depending on whether its core assumption fits you.

Best for: lifters who know their body-fat percentage and have a history of overestimating their burn.

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The results, side by side

Same woman. Five reputable calculators. Here's the damage:

Calculator	Formula	If she picks "light"	If she picks "moderate"
tdeecalculator.net	undisclosed	~2,056	~2,318
calculator.net	Mifflin-St Jeor	2,056	2,318
tdee.is	Mifflin-St Jeor	2,056	2,318
Hers	Mifflin / HB / Katch	~2,056	~2,398
Legion	Katch-McArdle	1,729	1,945

Full spread: 1,729 to 2,398 kcal — about 670 calories a day, a 39% swing.

Two things stand out. First, the BMR formulas barely disagree — Mifflin, Harris-Benedict, and Katch-McArdle put her resting burn within about 100 calories of each other. Nearly the entire spread comes from the activity multiplier, i.e., from a dropdown the user has to answer with a guess. Second, even within a single calculator, the light-vs-moderate guess alone moves her number by ~260 kcal — half a typical weight-loss deficit, decided by vibes.

If you want the full math on why this happens (and how to decompose your burn into BMR + NEAT + TEF + EAT to escape the dropdown entirely), we wrote a whole deep-dive: Why TDEE Calculators Disagree by 800 Calories — and How to Fix It.

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What none of the top 5 do

For weight loss specifically — the thing you searched for — every one of these tools shares four blind spots:

1. They're one-shot estimates. Your TDEE drops roughly 30 kcal for every kilogram you lose. Lose 10 kg and the number you started with is now ~300 calories stale — but no calculator follows up, recalculates, or even reminds you to come back.
2. They can't see your actual life. Steps, commute, job type, cooking, chasing kids around — all of it gets crushed into one dropdown. A desk worker with two toddlers and a desk worker who DoorDashes every meal pick the same "sedentary" option and get the same number. They do not have the same TDEE.
3. No GLP-1 awareness. If you're on Ozempic, Wegovy, Mounjaro, or Zepbound, the generic "eat 500 below maintenance" advice doesn't fit — appetite suppression often lands you 600–900 below maintenance without trying, and the real risks shift to under-eating and protein. None of the top five adjust for this (including, oddly, the one owned by a GLP-1 telehealth company).
4. No feedback loop. When the scale disagrees with the calculator in three weeks — and for roughly a third of people, it will — there's no way to find out which input was wrong. You just start over with a different guess.

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How to actually use a TDEE calculator to lose weight

Whichever tool you choose, the process that works is the same:

1. Get your maintenance number — and when the activity dropdown makes you hesitate, pick the lower option. Overestimating activity is the single most common reason "eating at a deficit" doesn't produce weight loss.
2. Subtract 250–500 calories. That targets 0.25–0.5 kg (0.5–1 lb) per week — fast enough to see progress, slow enough to keep muscle and sanity. Skip the "extreme" tiers; never go below ~1,200 kcal without medical supervision.
3. Hold that intake for 2–3 weeks and track your weight. Daily weigh-ins, weekly averages — daily fluctuations are water and noise.
4. Adjust based on reality, not the calculator. Losing ~0.5 kg/week? The estimate was right. Losing nothing? Your true TDEE is lower than estimated — drop 150–200 calories. Losing much faster than planned? Add some back.
5. Recalculate every 5 kg lost. Your maintenance falls as you shrink; the deficit that worked at 80 kg quietly evaporates at 70 kg. This is the step everyone skips, and it's why plateaus feel mysterious when they're mostly arithmetic.

Do those five steps with any calculator on this list and you'll beat the average dieter. Steps 3–5 are where the weight loss actually happens; the calculator only buys you a decent starting guess.

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Why we built ours differently

Full disclosure: NanoRhino makes an AI nutrition coach, and our free TDEE calculator is how many people first find us — the same funnel structure as Hers and Legion, plainly stated.

Here's what we changed, based on everything above:

• No activity dropdown. It's a short conversation — five-ish questions about how you actually live: your job, your steps, your commute, your cooking, your workouts. It builds your number from the components (BMR + NEAT + TEF + EAT) instead of one multiplier.
• It shows its work. You get a labeled breakdown of where every calorie goes, plus a comparison against what the traditional dropdown method would have told you — so when something looks off, you can see which piece to challenge.
• A range, not false precision. You get a band with a recommended target deliberately biased toward the low end, so your deficit survives even if your activity estimate was optimistic.
• It knows about GLP-1s. Tell it you're on Ozempic or Zepbound and the guidance changes — your maintenance number becomes a reference line, not an eating target, and the focus shifts to protein and not under-eating.
• Ask "what if." After your result, ask "what if I walked 12,000 steps?" or "what if I lifted three times a week?" and it recalculates on the spot. Volunteer a goal weight and it projects a realistic timeline.
• A completely free TDEE calculator — no signup, no email required. It runs online in your browser, and the result is yours in about five minutes.

→ Try the NanoRhino TDEE Calculator

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FAQ

What is the best free TDEE calculator? All five calculators reviewed here are free to use online, no payment required. The differences are in what surrounds the number: calculator.net and tdee.is are free with no email gate; Hers and Legion are free tools attached to paid products; ours is free with no signup and no email. If "free" to you also means "no funnel at all," tdee.is is the cleanest of the five.

Is a TDEE calculator the same as a calorie calculator? Essentially, yes. A TDEE calorie calculator estimates your Total Daily Energy Expenditure — the calories you burn per day — which is the maintenance number every calorie calculator is built around. "Calorie calculators" usually go one step further and subtract a deficit for you; with a plain TDEE number, you subtract the 250–500 yourself.

Which TDEE calculator is the most accurate? None of them, individually — every formula carries ±10% error, and the activity guess adds more. The most accurate process is: take any estimate as a starting hypothesis, eat consistently for 2–3 weeks, and let your scale trend correct the number. Calculators that show their components (tdee.is, ours) make that correction far easier than black-box ones.

How many calories below TDEE should I eat to lose weight? 250–500 below maintenance for most people (≈0.25–0.5 kg per week). Legion's 20–25%-below-TDEE rule lands in a similar place for most bodies. On a GLP-1, don't force a number — track that you're not chronically under-eating protein and calories instead.

Why does every TDEE calculator give me a different number? Mostly the activity multiplier, not the BMR math. The three standard BMR formulas agree within ~100 kcal; the activity dropdowns disagree by 300–600+. Our test showed a 670-calorie spread on one person. Full explanation here.

Should I eat back the calories I burn exercising? No. If your TDEE estimate included your workouts (every calculator here asks about exercise), those calories are already in the number. Eating them back double-counts them and erases your deficit.

Do I need to recalculate my TDEE as I lose weight? Yes — every 5 kg (≈10 lb). Maintenance drops roughly 30 kcal per kilogram lost. A static number from the day you started is the most common hidden cause of a "plateau."

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Closing note

All five of these calculators will get you a usable starting number, and the review table above should tell you which fits how you think. Just remember what a TDEE calculator can and can't do: it can give you a hypothesis. The weight loss comes from testing it.

If you'd rather have a tool that builds the number from your real life, shows every assumption, and answers "what if?" — our free Accurate TDEE Calculator is one conversation away. No signup, no email.

Built with care by Link Heart Limited in Houston, Texas.