Hydrology Formulator vs Activity Block
Price, ratings, monetisation and update history for both apps, side by side — with what reviewers say about each.
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.
- 1,000+ formulas and calculators
- Groundwater analysis tools
- Stormwater design calculations
- Open channel and pipe flow equations
- Water pollution modeling
- Conversions and reference data
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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
Activity Block
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Effortlessly manage daily tasks, stay organized, and boost productivity with Activity Block. Simplify your routine and achieve more every day!
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Verdict
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
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.
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.
| Parameter | Hydrology Formulator | Activity Block |
|---|---|---|
| Price | Free — better | $0.99 |
| Rating | 5.0 (1 ratings) — better | — |
| Positive reviews | 0.0% of reviews | — |
| Number of ratings | 1 — better | — |
| Update frequency | Every 6 months — better | Every 14 months |
| Ads | No | No |
| In-app purchases | Yes | No — better |
| Monetization | Free | — |
| Devices | iPhone, iPad | iPhone, iPad |
| Requires iOS | 18.6 | 16.4 — better |
| Further details — not scored | ||
| Size | 18 MB | 1 MB |
| Age rating | 4+ | 4+ |
| Developer | Historycentral.com | Luciano Souto |
In-app purchases
Hydrology Formulator
- Pro Version$3.99
Activity Block
No in-app purchases
Questions
Is Hydrology Formulator free?
Is Activity Block free?
Do Hydrology Formulator or Activity Block have ads?
Which is updated more often, Hydrology Formulator or Activity Block?
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