Old School RuneScape Loot Calculators — Barrows EV, Unique Drop Chance & GPH
Use the Barrows Loot Calculator to model expected value (EV) per run, gold per hour (GPH), and the probability of getting at least one unique over multiple chests. This page explains the math, shows how to tune time-per-run and costs, and links to deeper guides and glossary terms.
OSRS Barrows Calculator Quick Start — EV per Run, Unique Probability & GPH
Start with the example setup, then adjust time per run, consumable costs, and optional price overrides. Results update live and can be shared via the copy-link button on the calculator. If you're new to EV and GPH, skim our EV vs GPH primer first.
Inputs & Defaults
Inputs include time per run (seconds), chest open/close time, item prices, and optional death & potion costs. You can also tweak the Barrows unique rate via overrides for testing. Prices are pulled from community snapshots and may be rounded for stability.
Outputs & Key Metrics
The calculator shows EV/run, GPH (EV × runs/hour), P(any) (union probability across runs), and helpful notes on assumptions. Use the union probability model when you want the odds of seeing at least one unique over a series of runs.
Shareable Setups & URL Params
Your configuration is encoded in the URL so you can share routes with friends or come back later. This is great for benchmarking different time costs or price assumptions side-by-side.
Example — 180s runs, baseline prices
With 180-second runs and default prices, you'll typically see steady EV/run but a modest GPH. Shaving travel time or loot-handling usually lifts GPH much faster than chasing tiny EV bumps.
Formula recap
EV = Σ(outcome value × probability). GPH = EV/run × runs/hour. See also EV and variance.
See also
- Binomial distribution for k-success modeling.
- Confidence interval if you're validating with sample runs.
OSRS Drop Rate Math Explained — Union Probability & Binomial Trials
Barrows uniques are typically modeled as independent trials per chest. If the per-chest unique probability is p, then the chance of getting at least one unique across n chests is:P(any) = 1 − (1 − p)^n. This is the union probability.
Expected Value (EV) for Barrows
EV includes unique expected value + rune/etc. expected value − costs. Costs include consumables, travel time, and optional death tax. Because Barrows has many low-value outcomes and a few high-value uniques, variance is meaningful; don't confuse a good EV with guaranteed payouts.
"At Least One Unique" — Worked Example
Suppose p = 5.8% per chest. Over 25 chests, P(any)=1−(1−0.058)^25≈77%; over 50 chests, it rises to ~94%. Use the calculator's P(any) readout to plan expectations over weekends or leagues.
Confidence Intervals from Sample Runs
Testing a new route? Record n runs and derive a 95% CI on your observed drop rate or EV. As a rule of thumb, CI width shrinks ~ 1/√n. See the confidence interval entry for methods and caveats.
Caveats — independence & pity
Barrows doesn't use pity. If a game system uses soft/hard pity, the independent-trial assumption breaks. Always verify the loot system details for the content you're modeling.
Sampling pitfalls
- Short sessions inflate variance and can make EV look "wrong" even when math is correct.
- Price swings during a league can skew backtests vs forward EV.
Related reading
Profit per Hour (GPH) & Route Optimization for Old School RuneScape
GPH is where time truly matters. Two routes can have identical EV/run but very different GPH due to travel time, chest animations, banking, or detours. Measure your real run time, not the "best-case" estimate from a perfect lap.
Time per Run vs EV per Run
Lowering time per run often beats chasing a small EV bump. If a 10% EV increase costs you 30% more time, your GPH falls. Keep your eyes on the hourly number.
Cost Modeling — Consumables & Deaths
Consumable usage adds up. Use the cost fields (pots, food, teleports) and include an honest death estimate per hour if relevant. Your goal is to compare net GPH, not theoretical gross.
Benchmarks & Shareable Routes
Use the "copy link" button in the calculator to share exact inputs for community feedback. If your route improves, preserve both versions to document the uplift in time or EV separately.
Example — shaving 20s per run
Cutting 20 seconds off a 200-second run (+10% runs/hour) lifts GPH even if EV/run is unchanged. This is why movement optimizations are king for currency/hour.
Tools
- GPH definition and usage notes
- Barrows Loot Calculator
Pro tip
Separate "speed" tests from "value" tests. First minimize run time; then, at that time budget, test value-increasing tweaks (gear swaps, inventory changes).
Data Sources, Assumptions & Limitations
We combine accepted drop tables with price snapshots and community research, then smooth volatility to keep calculators stable. Assumptions are listed in each calculator's methodology block and updated when leagues or balance changes land.
Price Snapshots & Overrides
Prices fluctuate. For repeatable routes, use overrides to test sensitivity; list your price source and date when sharing screenshots.
Drop Table References
We track public wikis, community sheets, and test runs. If you spot a discrepancy, open an issue with evidence and we'll re-evaluate the inputs.
Variance, Dry Streaks & Reality
EV is an average, not a guarantee. Long dry streaks happen even on well-understood content. Understand your bankroll and session variance before over-committing.
Known Limitations
- Prices and drop rates can change mid-league.
- Player-to-player skill varies; your time per run may differ from examples.
Where to learn more
Contact
Have data to share? Reach us via the Contact page.