[CALCULATOR]
How much fuel today actually asks for.
[WHAT THIS DOES]
Carbohydrate requirement scales with training load far more than any other macro does. A lifter trains well on around 3 g/kg; an athlete running forty miles a week may need 6 to 8 g/kg on hard days. This gives the range for your bodyweight and today’s session.
Why carbohydrate is the macro that moves
Set protein from bodyweight. Set fat as a share of calories with a floor. Let carbohydrate take the remainder.
That ordering is the whole answer for a hybrid athlete, and it is not arbitrary. Protein requirements barely change with endurance volume. Fat requirements are driven by hormonal function and fat-soluble vitamin absorption, not by training load. Fuel demand changes enormously.
So carbohydrate is the only macro that should move when your training moves — and setting it last is what makes that happen without you recalculating anything.
Fix carbs at a percentage of calories instead, and adding a long run silently takes calories out of protein and fat too. Which is precisely backwards.
The bands
| Day | g/kg | Why |
|---|---|---|
| Rest, or easy under 60 min | 3–4 | Glycogen is not the limiter |
| Lifting only, or easy 60–90 min | 4–5 | Enough to train well |
| Lifting plus endurance, or one hard session | 5–7 | Two stresses in one day |
| Long session over 2 h, or a doubled day | 7–9 | Glycogen is the limiter |
| Race, or a very long session | 8–10 | Top up the day before too |
For an 82 kg athlete that is a range from 245 g on a rest day to over 800 g on a race day. No fixed percentage handles that span, which is the practical reason the ordering matters.
What under-fuelling actually costs, and when
The part hybrid athletes get wrong, because the bill arrives somewhere unexpected.
Training on low glycogen costs more recovery for the same adaptation. For a pure endurance athlete that shows up on the next run. For a hybrid athlete it shows up in the gym, two days later.
Muscle glycogen takes 24 to 48 hours to refill with adequate carbohydrate — longer without it. A depleted Saturday long run leaves Monday's heavy session running on a substrate deficit, and that feels exactly like being weak:
- Warm-up weights feel heavier than they should
- Sets that should be at 2 RIR come out at 0
- The last set is a grind at a load you handled last week
The conclusion is usually "my recovery is poor" or "the block is too aggressive" or "interference is real". The actual cause was a Saturday nutrition decision, and nothing about Monday was wrong. The full chain.
Carbohydrate periodisation, practically
More on hard days, less on easy ones, protein and fat held constant. Well supported, and completely impractical if it means re-planning a day every morning.
Two saved day templates makes it a habit rather than a project:
| Training day | Rest day | |
|---|---|---|
| Protein | 180 g | 180 g |
| Fat | 85 g | 85 g |
| Carbohydrate | 430 g | 300 g |
| Total | ~3,200 | ~2,680 |
One tap each. That is the difference between periodisation being a good idea and being something you actually do.
What this calculator does not tell you
Your total calorie target. That comes from your measured maintenance plus or minus your goal, and it should be measured rather than predicted — a trained lifter's usable surplus is about 179 kcal a day, which is smaller than the error on any prediction. The method.
Intra-session fuelling. Over 90 minutes you need 30 to 60 g per hour, rising toward 90 with a glucose-fructose mix for efforts over two and a half hours — and gut tolerance for that is itself trainable over weeks.
What to do next
Build two day templates with protein and fat identical and carbohydrate carrying the difference. Then stop making this a daily decision.
Questions
How many carbs does a hybrid athlete need?
It depends almost entirely on the day. Around 3 to 4 g per kilogram on a rest day, 5 to 7 on a day with both lifting and endurance work, and 7 to 9 on a long session or a doubled day. For an 82 kg athlete that is a range from about 245 g to over 700 g.
Should I eat fewer carbs on rest days?
Yes, if you are periodising — hold protein and fat constant and let carbohydrate carry the difference. What you should not do is turn a rest day into an energy deficit, because the adaptation from your training happens on the rest day.
Do carbs make you gain fat?
Excess total energy does. Carbohydrate specifically does not, and for an athlete training twice a day it is the macro fuelling the work. What matters is whether the day total sits above or below your measured maintenance.
How do I know if I am under-fuelling?
The clearest sign in a hybrid athlete is a lifting session that feels heavy for no reason one to two days after a long endurance session. That is partly refilled glycogen, and it is routinely misdiagnosed as poor recovery or as interference.