Presented by Zia H Shah MD

Abstract

Using Pew Research Center’s global religious-demography projections as the anchor, a reasonable central estimate is that around one‑third of the world’s people could be Muslim by 2090, implying a global Muslim population on the order of ~3.5 billion. Pew’s published work formally projects to 2050, but it also includes a clearly labeled extension of its main model beyond 2050 showing Muslim share rising to the mid‑30% range by 2100.
To translate “share” into “people” for 2090, I combine that Pew share trajectory with the UN World Population Prospects 2024 probabilistic projection for total world population in 2090.
Framed as scenarios: a bearish (lower) outcome lands near ~3.2B, a most likely outcome near ~3.5B, and a bullish (higher) outcome near ~3.8B Muslims in 2090—driven mainly by uncertainty in global population totals and, secondarily, by how fast Muslim fertility/age-structure advantages converge with the rest of the world.

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What Pew actually projects (and what it implies for 2090)

Pew’s “hard stop” projections through 2050

Pew’s 2015 report projects the Muslim population to grow from ~1.6 billion (23%) in 2010 to ~2.8 billion (30%) in 2050, driven largely by younger age structure and higher fertility.

Pew also emphasizes that its projections account for the geographic distribution of religions, age structure, fertility and mortality, migration, and religious switching.

Pew’s “Beyond 2050” extension (crucial for 2090)

Pew explicitly says it stops at 2050 because the farther out you go, the more unforeseen events can alter trajectories—but it also provides an illustrative extension of its main model beyond 2050.

In that extension:

• Around 2070, the Muslim share is shown reaching ~32% (rough parity with Christians).
• By 2100, Pew indicates Muslims at roughly ~35% of world population (slightly more than Christians).

Converting Pew’s long-run “share” into a 2090 “share”

Pew doesn’t publish a single, explicit “Muslim share in 2090” figure in the text—so for 2090 I estimate the share by interpolating between Pew’s ~32.3% (2070) and ~34.9% (2100) values shown in the Pew chart.

That produces an estimated Muslim share in 2090 of ~34.0% (about 34.03%).

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Converting share into people: UN world population totals for 2090

To turn “~34% Muslim” into a headcount, we need a world population total for 2090.

The UN World Population Prospects 2024 probabilistic outputs (median and prediction intervals) give world population in 2090 (mid‑year, “as of 1 July”) of:

• Median (most likely): ~10.27 billion
• Lower 80% bound: ~9.64 billion
• Upper 80% bound: ~10.95 billion

(For context, UN messaging also describes global population peaking around ~10.3 billion in the mid‑2080s and then edging down slightly by 2100. )

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Scenarios for global Muslim population in 2090

How to read these

• Most likely = UN median world population × Pew-implied 2090 Muslim share (~34.0%).
• Bearish = lower world population path + slightly slower rise in Muslim share.
• Bullish = higher world population path + slightly faster rise in Muslim share.

Pew itself warns that disaffiliation becoming common in large Muslim populations could slow or reverse Muslim growth in share, which is why I include a modestly lower “bearish” share assumption.

Results (rounded)

Scenario (2090)	World population (UN)	Muslim share assumption	Muslim population (result)
Bearish	~9.64B (lower 80%)	33% (slower share growth than Pew-implied midpoint)	~3.18B
Most likely	~10.27B (median)	~34.0% (interpolated from Pew 2070→2100 extension)	~3.50B
Bullish	~10.95B (upper 80%)	35% (roughly Pew’s 2100 level reached earlier)	~3.83B

A tighter “Pew-share-only” range (if you prefer fewer assumptions)

If you hold the ~34.0% share constant across the UN 80% world-population bounds, the implied 2090 Muslim population range is roughly ~3.28B to ~3.73B (with ~3.50B at the median).

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Why the scenarios differ: what pushes 2090 lower or higher

Forces that make the 2090 Muslim total lower (bearish direction)

• Faster fertility convergence in Muslim-majority countries (fertility falling toward or below replacement sooner than Pew’s continuation-of-trends picture).
• Higher disaffiliation/weakening religious retention in countries with large Muslim populations—explicitly noted by Pew as a trajectory‑changer.
• Lower overall world population than the median UN path (which mechanically reduces every group’s absolute size).

Forces that make the 2090 Muslim total higher (bullish direction)

• Sustained youthful age structure and above-average fertility in key regions where Muslims are concentrated, so the share continues to rise into the mid‑30s as Pew’s extension suggests.
• Higher total world population than the median path (again, raising the absolute counts).

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Thematic epilogue

Demographic projections are never just math; they’re a mirror held up to today’s patterns of family size, education, health, migration, and identity. Pew’s core finding—Muslim populations growing rapidly through the mid‑century and rising toward roughly a third of the world over the longer run—rests on a simple, human engine: births minus deaths, amplified by age structure.

But by 2090, the story is less about one religion “winning” and more about how billions of people live, learn, work, and belong. The same forces that raise living standards—girls’ education, urbanization, economic security, health care—also tend to compress fertility and reshape what religious identity means across generations. Pew openly flags that shifts like widespread disaffiliation in Muslim societies could bend the curve.

So the most responsible way to hold these numbers is as plausible horizons, not destiny: ~3.5 billion Muslims in 2090 as the center of gravity, with a realistic envelope that can slide lower or higher depending on how the next two generations navigate modernity, continuity, and change.