Comparison

Hydrology Formulator vs Activity Block

Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.

Head to head
About

Hydrology Formulator

This app provides a comprehensive collection of over 1,000 formulas, calculators, and conversions for hydrology and civil engineering. It covers a wide range of topics including groundwater, stormwater, pipe flow, and water pollution.

Highlights
  • 1,000+ formulas and calculators
  • Groundwater analysis tools
  • Stormwater design calculations
  • Open channel and pipe flow equations
  • Water pollution modeling
  • Conversions and reference data
Features
Read full description

HYDROLOGY FORMULATOR is the ultimate pocket reference for hydrologists, civil engineers, environmental scientists, and students. Packed with 1,000+ formulas, calculators, and conversions, it covers everything from groundwater analysis to stormwater design — all in one powerful app. HYDROLOGY CALCULATORS Infiltration & Recharge — 17 Calculators - Porosity, Green-Ampt Infiltration, Horton Infiltration, Philip Infiltration, Holtan's Model, Hydraulic Conductivity, Groundwater Recharge, Mean Pore Velocity, Specific Discharge, Volumetric Water Content, and more Evaporation & Transpiration — 8 Calculators - Penman-Monteith ET0, Blaney-Criddle ET, Thornthwaite PET, Crop Evapotranspiration, Saturation Vapor Pressure, Evaporation Rate of Lake, Relative Humidity, Potential Evapotranspiration Open Channel Flow — 12 Calculators - Manning's Equation (SI & US), Chezy Equation, Froude Number, Hydraulic Radius, Hydraulic Jump, Critical Depth, Specific Energy, Reynolds Number, and more Pipe Flow — 7 Calculators - Darcy-Weisbach Equation, Hazen-Williams Velocity (SI & US), Reynolds Number, Water Hammer Pressure, Continuity Equation, Minor Head Loss Stormwater & Watershed — 9 Calculators - SCS Curve Number Runoff, SCS Peak Discharge, IDF Rainfall Intensity, Kirpich Time of Concentration, Gumbel Extreme Value, Detention Storage Volume, Composite Curve Number, and more Pumps & Water Supply — 7 Calculators - Total Dynamic Head, Water Horsepower, Brake Horsepower, NPSHa, Affinity Laws for Flow, Head, and Power Weirs & Orifices — 6 Calculators - Rectangular Weir (SI & US), V-Notch Weir, Broad-Crested Weir, Orifice Flow, Spillway Discharge Water Flow — 10 Calculators - Water Flow Rate, Velocity of Water, Volume of Water Flow, 90° V-Notch calculations, Pipe Total Diameter, and more Surface Runoff — 6 Calculators - Average Velocity, Runoff, Travel Time, Hourly Rate of Rainfall Groundwater — 7 Calculators - Darcy's Law, Thiem Equation, Cooper-Jacob Drawdown, Dupuit Well Flow, Radius of Influence, Storage Properties Soil Pollution — 5 Calculators - Groundwater Pore Velocity, Effective Diffusion, Hydrodynamic Dispersion, Aquifer Parameter, Variance of Pore Velocity River Pollution — 7 Calculators - River Oxygen Deficit, Critical Time & Distance for Oxygen Deficit, Re-Aeration Constants, Dissolved Oxygen, River Flow, Water Temperature Lake Pollution — 4 Calculators - Waste Entering, Equilibrium Concentration, Settling Loss Rate, Particle Deposition Rate Sediment Transport — 4 Calculators - Shields Parameter, Bed Shear Stress, Stokes' Law Settling Velocity, Meyer-Peter Müller Bedload Snow Hydrology — 2 Calculators - Snow Water Equivalent, Degree-Day Snowmelt Culvert Hydraulics — 2 Calculators - Culvert Headwater (Outlet Control), Culvert Outlet Control Head Loss Flood Routing - Muskingum Routing Water Balance - Water Balance Equation, Storage Continuity Plus: Area Formulas, Pollution Cleanup, and more CONVERSIONS & REFERENCE Hundreds of built-in conversions across 16 categories including: - Liquid Measures, Cubic Measures, Linear Measures, Square Measures - Flow Rates, Pressures, Horsepower, BTU, Watts, Power - Hydraulic Conversions, Sand-to-Volume, Ft-Lbs - 8 Temperature Scales (Celsius, Fahrenheit, Kelvin, Rankine, Réaumur, Newton, Delisle, Rømer) - Metric Conversions and Fraction Conversions KEY FEATURES - Save and review past calculations - Switch between US (Imperial) and Metric units - Clean, intuitive interface designed for field and office use - Premium upgrade unlocks Groundwater, Pollution, Sediment Transport, Snow Hydrology, Culvert Hydraulics, and Flood Routing calculators

About

Activity Block

Features
Read full description

Effortlessly manage daily tasks, stay organized, and boost productivity with Activity Block. Simplify your routine and achieve more every day!

Screenshots

Hydrology Formulator4 screens

Verdict

The call

The clearest difference is price: Hydrology Formulator at Free against Activity Block's $0.99. Hydrology Formulator also leads on update cadence (every 6 months vs every 14 months). Activity Block's advantage is in-app purchases (none vs 1) and iOS requirement (16.4 vs 18.6). On ads and device support there is nothing between them.

Scored on Price · Rating · Positive reviews · Number of ratings · Update frequency · Ads · In-app purchases · Monetization · Best chart rank · Devices · Requires iOS

CostPrice · In-app purchases · Ads · Monetization

Hydrology Formulator is free to download; Activity Block costs $0.99 up front. Hydrology Formulator sells 1 one-off in-app purchase. Activity Block asks for nothing beyond the download.

UpkeepUpdate frequency

Hydrology Formulator ships an update every 6 months, Activity Block every 14 months. The most recent releases landed on October 8, 2026 and October 7, 2026 respectively.

Scorecard4 real differences · 6 level
Hydrology Formulator versus Activity Block: the parameters behind the verdict, then further details
ParameterHydrology FormulatorActivity Block
PriceFree — better$0.99
Rating5.0 (1 ratings) — better—
Positive reviews0.0% of reviews—
Number of ratings1 — better—
Update frequencyEvery 6 months — betterEvery 14 months
AdsNoNo
In-app purchasesYesNo — better
MonetizationFree—
DevicesiPhone, iPadiPhone, iPad
Requires iOS18.616.4 — better
Further details — not scored
Size18 MB1 MB
Age rating4+4+
DeveloperHistorycentral.comLuciano Souto

In-app purchases

1 purchases

Hydrology Formulator

One-time1
  • Pro Version$3.99
None

Activity Block

No in-app purchases

Questions

Is Hydrology Formulator free?
Hydrology Formulator is free to download, with in-app purchases available.
Is Activity Block free?
Activity Block costs $0.99, with no in-app purchases.
Do Hydrology Formulator or Activity Block have ads?
Neither Hydrology Formulator nor Activity Block shows ads.
Which is updated more often, Hydrology Formulator or Activity Block?
Hydrology Formulator ships an update every 6 months, and Activity Block every 14 months. Most recently, Hydrology Formulator was updated on October 8, 2026 and Activity Block on October 7, 2026.

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