About Mana on Curve

How the simulation works, what it models, and how to control it from your decklist.

Usage

Export a decklist from MTG Arena or your favorite deck site.
Paste it into the Decklist box on the home page.
Optionally open Simulation Options to tune mulligans, play/draw, and run count.
Press Simulate and read the per-card on-curve rates and failure modes.
Press Copy link to share your exact inputs with someone else.

How a Trial Works

Each simulation draws an opening hand, applies the London mulligan strategy, then draws cards up to the deck's highest target turn (its curve window). Every non-land is scored on its intended cast turn — by default its mana value, so a 3-mana spell is aimed at turn 3. For each copy of the card the simulation asks, in order: did you have enough total mana for the cost, could you pay the colored requirements with the mana available (accounting for lands that enter tapped or otherwise come online late), and was the card actually in hand? The first check that fails classifies the outcome as not enough lands, color / timing, or undrawn; passing all three counts as on curve. Trials do not play out a full game beyond that curve window.

Reading the Results

CMC (converted mana cost): The total mana value of a spell. For example, {2}{R} has CMC 3 (generic 2 + one red).
On curve: The share of trials where you cast the card on its intended turn — enough lands, the right colors, and the card in hand when you needed it.
Mana|CMC: Conditional: among trials where you already had enough total mana for that CMC on the cast turn, how often you could also pay the colored (and timing) requirements. A high Mana|CMC with a low on-curve rate usually means the card was undrawn or mulliganed away — or that you were often short on lands, since the on-curve rate also depends on how often you hit enough total mana.
(T#): The turn the simulation aims to cast the card. By default that is the card's mana value; a T= decklist modifier can shift it (the value is added to the default, so T=1 on a 3-mana spell aims it at turn 4).
Failure columns: Not enough lands, color / timing, and undrawn are the three ways a cast can fail. They match the funnel below and the segments in the Easiest to Hardest to Cast on Curve chart on the results page. On its turn, each copy runs through the same checks; the first check it fails decides the outcome.

What happens to each copy of the card on its turn (T#)

Enough total mana for CMC?Not enough landstotal − cmc

Right colors + timing?Color / timingcmc − mana

Card in hand?Undrawnmana − play

On curveplay

The four outcomes cover every trial (they add up to 100%) and match the colors in the Easiest to Hardest to Cast on Curve chart on the simulator results page.

What It Models

The London mulligan, including the mulligan-to floor and land-count keep rules.
On the play vs on the draw.
Cards that cost multiple or hybrid colors of mana.
Lands that produce multiple colors, and lands whose mana is delayed by entering tapped or having other timing conditions.

Simplifying Assumptions

The only card draw is the normal draw step each turn.
A non-land is scored only on its own target turn — trials do not play out a full game beyond the curve window.
Cost-reducers and alternative costs (convoke, delve, Phyrexian mana, etc.) are not simulated.
Effects that change the mulligan or starting hand (e.g. Serum Powder) are not simulated.

The goal is a sensible baseline for tuning your land count and mana base — not a perfect model of every card interaction. Use your judgment when interpreting the results.

Advanced: Decklist Modifiers

Append a modifier to the end of any card line in your decklist to override how that card is simulated:

T=1 — shift the target turn. The value is added to the default (mana value) turn, so T=1 on a 3-mana spell aims it at turn 4.
M={R}{G} — force the card to act as a mana source producing the given colors (use M=auto to reuse a land face). Useful for mana dorks like Llanowar Elves. The card is then treated as an unconditional source, so read those results with care.
X=4 — set the value of an {X} cost (defaults to 1).

Acknowledgments

Simulation engine: landlord-ts, a TypeScript port of the Rust landlord engine.
Card data and art from Scryfall.