M-Ratio Calculator

How to use it

M = stack ÷ (small blind + big blind + antes per orbit). The calculator also gives effective M — M scaled for table size — and drops you into the right Harrington zone with a one-line plan.

The Harrington zones

Green (20+): deep enough to play a full game. Yellow (10–20): tighten and hunt for spots. Orange (6–10): shove-or-fold takes over; stop limping. Red (1–5): first-in push with any reasonable hand. Dead (<1): you're committed on the next hand — take the first playable holding.

Why M beats counting big blinds

Big-blind counts ignore antes, which quietly speed up short-stack play in the late stages. M folds the antes in, so it reflects true urgency. Learn more in tournament strategy and short-stack push/fold.

Effective M vs M

Plain M asks a simple question: if you folded every hand from here, how many full orbits could you sit through before the blinds and antes bled you out? But that question quietly assumes a full table. At a short-handed table the blinds reach you far more often per hand, so a given M buys you fewer real decisions than the same M would nine-handed. Effective M corrects for this: effective M = M × (players ÷ 10).

The intuition is straightforward. At a 10-handed table you post the blinds once every ten hands, so effective M and M are essentially the same. Six-handed, the blinds arrive nearly twice as fast, and effective M shrinks to about 60% of M. Heads-up you are in a blind every single hand, so effective M collapses to roughly a fifth of M — an M of 10 heads-up is genuinely a push-or-fold situation even though the raw number looks comfortable. Whenever the table is short — a final table, a fast satellite bubble, or heads-up play — trust the effective M, because it reflects how quickly the clock is actually ticking. The calculator above reports both so you never have to guess which one applies.

How antes and format shift the zones

The Harrington boundaries — green ≥ 20, yellow 10–20, orange 6–10, red 1–5, dead under 1 — are fixed, but the speed at which you fall through them is not. In the early levels of most tournaments there are no antes, so the orbit cost is just the small blind plus the big blind and M drains slowly. Once antes kick in, every player is feeding the pot each hand and the orbit cost jumps — often by half again or more at a full table — so the same stack that showed a comfortable M an hour ago can quietly slip from yellow into orange without you losing a single pot. Rising blind levels compound this: your chip stack may be flat while your M steadily falls, which is the real reason late-stage play tightens into shove-or-fold.

Format changes your attitude to the zones more than the numbers. In a freezeout, busting ends your night, so you generally respect the zones and look for clean spots to accumulate before red. In a re-entry or rebuy event, especially while re-entries are still open, the cost of busting is far lower, so many players treat a yellow or orange M more aggressively — taking thinner shoves and marginal gambles because a bust simply means firing another bullet. The M is the same; the risk of ruin behind it is not. As you approach the money or a pay jump, layer in ICM pressure too — see the ICM calculator — because survival can be worth more than chips even when your M says push.

A worked example

You have a 12,000 stack at 200/400 with a 50 ante, nine-handed. The orbit cost is the small blind plus big blind plus antes from all players: 200 + 400 + (50 × 9) = 1,050. So M = 12,000 ÷ 1,050 ≈ 11.4 — squarely in the yellow zone. Effective M at nine-handed is 11.4 × (9 ÷ 10) ≈ 10.3, close to raw M, so you tighten up, stop entering pots by limping, and start hunting for a strong spot to be first-in.

Now the table breaks and you are four-handed at the same level. The orbit cost falls because only four players post antes: 200 + 400 + (50 × 4) = 850, so raw M rises to 12,000 ÷ 850 ≈ 14.1. That looks better — but effective M is 14.1 × (4 ÷ 10) ≈ 5.6, which is orange, bordering red. Despite the higher raw M, the blinds are hitting you so often that you should already be firmly in shove-or-fold mode. This is exactly the trap effective M exists to catch.

Common M mistakes

The mistakes cluster in a few predictable places:

• Forgetting the antes. Counting only the blinds in the orbit cost overstates your M and lulls you into playing too passively while your stack is actually melting.
• Ignoring effective M at short tables. Raw M can look healthy heads-up or four-handed while effective M screams push-or-fold — always read the adjusted number when the table shrinks.
• Waiting for a premium in the red zone. At M 1–5 you cannot afford to fold into oblivion; the correct play is to be first-in aggressively with any reasonable hand rather than blinding down to nothing.
• Treating M as the whole story near the money. M measures survival against the blinds, not the pay ladder — pair it with ICM thinking on the bubble and at final tables.

Get comfortable estimating M at the table and it becomes a running gauge of urgency; the short-stack push/fold guide covers the shoving ranges each zone calls for.

Frequently asked questions

What is the M-ratio in poker?

The M-ratio (or M) is how many orbits you can survive before the blinds and antes eat your stack, if you fold every hand. It equals your stack divided by the total cost of one orbit — the small blind, big blind and all antes. It's the core measure of urgency in tournaments, from Dan Harrington's Harrington on Hold'em.

How do you calculate M?

M = stack ÷ (small blind + big blind + total antes per orbit). If antes are posted by each player, multiply the ante by the number of players. A 12,000 stack at 200/400 with a 50 ante at a 9-handed table has an orbit cost of 200 + 400 + 450 = 1,050, so M ≈ 11.4.

What is effective M?

Effective M adjusts M for a short-handed table, because you pay the blinds more often when fewer players share them. Effective M = M × (players ÷ 10). At a full table it's about the same as M; heads-up it's roughly a fifth of it, reflecting how fast the blinds come around.

What are the Harrington M zones?

Green (M ≥ 20): full flexibility. Yellow (10–20): tighten up, start looking for spots. Orange (6–10): find a hand to shove, no more limping. Red (1–5): push-or-fold, first-in with any reasonable hand. Dead (under 1): you're all-in on the next hand you play, take the first decent spot.