How Many Aquatabs Does a Response Need? Forecasting Tablet Demand

Tony Miller

3 days ago

7 min read

Forecasting Aquatabs demand starts with population, not tablets. Multiply the people needing treated water by Sphere's 7.5 to 15 litre daily standard, convert litres to tablets at one per 8 to 10 litres, then add wastage and a caseload buffer before converting the total to weight and shipping volume.

What is the forecasting formula for Aquatabs demand?

The chain runs in one direction, and skipping a step is where procurement plans go wrong. Start with the target population, apply a treated-litres-per-person-per-day figure, multiply by the response duration to get total litres, divide by the tablet's rated treatment volume to get a base tablet count, then load two allowances on top: wastage and breakage in the supply chain, and a buffer against the caseload growing after the order is placed. Only the resulting number is converted to weight and shipping volume for a freight quote.

This is a procurement calculation, not a dosing guide. How many Aquatabs go into a single tank, jerrycan or tapstand is a separate, already-answered question; this piece treats that dosing rate as a fixed input, not a subject to re-argue.

How much water actually needs treating per person per day?

Less than the full Sphere figure, usually. Sphere/IFRC's WASH standards set total basic water needs at 7.5 to 15 litres per person per day, but that total splits into three uses: 2.5 to 3 litres for drinking and food, 3 to 6 litres for cooking, and 2 to 6 litres for hygiene. A household-level chlorination programme is normally dosed into the water people drink and cook with, not the water they wash or launder with, so the volume that actually needs a tablet is closer to the drinking-and-cooking band, roughly 5.5 to 9 litres per person per day, than to the full Sphere total.

Using the full 15 litre figure when only drinking and cooking water gets treated overstates the order by close to half. Using the 2.5 to 3 litre drinking-only figure understates it, because tablets are typically dosed into the whole jerrycan collected at the tapstand, cooking water included. A mid-range planning figure of around 7 litres per person per day, sitting inside the Sphere drinking-and-cooking band, is a defensible working assumption until field monitoring data says otherwise.

What treatment coverage and wastage allowance should a forecast include?

Two different allowances answer two different problems. Treatment coverage is the share of the target population you are actually procuring for, typically below 100% because distribution never reaches every household in a scattered or access-constrained population. Wastage and breakage covers loss inside the supply chain itself: foil strips damaged in transit, tablets exposed to humidity, cartons rejected on arrival.

A third factor belongs in the wastage line even though it looks like a coverage problem. Research on chlorinated water in South Sudan refugee camps found that 40 to 58% of households drawing from chlorinated tapstands had no detectable residual chlorine in their stored water, despite tablets having been distributed, and the researchers recommended raising the free residual chlorine target rather than assuming standard doses hold. That gap between tablets delivered and water actually protected is a real loss, and a forecast that ignores it runs short mid-response, sooner than the arithmetic suggested. An 8 to 10% combined allowance for transit wastage and field loss is a reasonable planning margin, a working assumption to check against your own distribution data, not an external statistic.

How long should the order cover, and why build in a caseload-revision buffer?

Long enough to reach a natural review point, not the full expected length of the outbreak. Cholera case curves move faster than procurement cycles. WHO AFRO reported that weekly cases in South Sudan's 2024-2025 outbreak fell from an average of 1,000 at the December 2024 peak to 114 in the last week of September 2025, alongside 8.6 million oral cholera vaccine doses administered against 87% of the targeted population. An order sized for the December peak would have been badly oversized by September; an order sized for a quiet month can be overwhelmed within weeks if a new transmission chain opens.

A ten to twelve week ordering horizon, with a scheduled review against actual caseload data, holds up better than either a short reactive order or a full-outbreak commitment. On top of the base calculation, add a caseload-revision buffer, typically 15 to 20%, sized to the volatility your context has actually shown. WHO's Disease Outbreak News DON579 recorded 71,825 suspected cholera cases and 1,194 deaths in South Sudan between 1 January and 17 August 2025 alone, a scale that outgrew most initial response plans, which is the argument for building the buffer in rather than waiting to raise a follow-on order once the caseload has already moved.

A worked example: forecasting for 40,000 people over ten weeks

Take a defined population of 40,000 and a ten-week (70-day) initial ordering horizon.

Coverage assumption: 90% effective reach, so 36,000 people are procured for.
Treated litres per person per day: 7 litres, inside the Sphere drinking-and-cooking band.
Daily treated volume: 36,000 x 7 = 252,000 litres.
Total litres over 70 days: 252,000 x 70 = 17,640,000 litres.
Base tablet count at one tablet per 8 litres, the conservative end of the 8 to 10 litre rated treatment volume for a 67mg Aquatabs tablet: 17,640,000 / 8 = 2,205,000 tablets.
Wastage and breakage allowance, 8%: 2,205,000 x 1.08 = 2,381,400 tablets.
Caseload-revision buffer, 15%: 2,381,400 x 1.15 = 2,738,610 tablets.

That is the number to put on a purchase order, roughly 2.74 million tablets for this population and this horizon. It is a fraction of what a large national response can require. SLS delivered more than 52 million Aquatabs tablets, treatment capacity exceeding 1 billion litres, during the 2024-2025 South Sudan cholera response, so an order of this size sits well inside proven pipeline capacity rather than at the edge of it.

How do you convert a tablet total into packs, cartons and a shipment?

Two figures, derived directly from the final tablet count, before you need a single carton size. The IFRC/ICRC Standard Products Catalogue lists a shipping weight of 0.0003kg and a shipping volume of 0.002 litres for a single 40mg-available-chlorine (67mg NaDCC) tablet. Multiplying those figures by the 2,738,610 tablets from the worked example gives a shipment of roughly 822kg and 5.5 cubic metres, the numbers a freight quote runs on, independent of how the tablets are packed.

Cartons and pallets sit on top of that weight and volume, not underneath it. Tablets ship in foil strips packed into cartons, and the strip count, carton count and pallet configuration vary by supplier and production lot, so the practical move is to request the current packing list with the quotation rather than assume a fixed carton size. Once the supplier confirms tablets per carton, the tablet total converts directly into a carton count, and the carton count into a pallet count for the truck or waybill you are booking.

Does an in-country buffer change how much safety stock you need?

Yes, because it changes what the buffer has to cover. A safety stock held to protect against a caseload revision only has to bridge the gap until the next order lands, and that gap is set by lead time. Stock ordered against Medentech's production and shipped from Ireland runs on a shipping and clearance timeline measured in weeks. Stock already held in Juba is a dispatch, not an import, and a buffer built to bridge days needs to hold far less volume than one built to bridge weeks.

That gap matters more now than it did two years ago. US foreign aid spending roughly halved, from around US$68 billion in 2024 to around US$32 billion in 2025, and a programme budget under that kind of pressure cannot afford to carry six weeks of safety stock against an origin lead time when an in-country distributor can cut the exposure to days. Forecast the tablet total, then decide the buffer against wherever the stock actually sits, not against the worst-case import timeline.

Frequently asked questions

How much water does one person need each day for calculating Aquatabs demand?

Sphere's total basic water need is 7.5 to 15 litres per person per day, split into 2.5 to 3 litres for drinking and food, 3 to 6 litres for cooking, and 2 to 6 litres for hygiene. Because household chlorination is usually dosed into drinking-and-cooking water rather than the full domestic supply, a forecast should generally use a figure closer to the 5.5 to 9 litre drinking-and-cooking band than the full total.

How many Aquatabs tablets treat one litre of water?

One 67mg Aquatabs tablet treats 8 to 10 litres of clear water with 30 minutes' contact time. This piece takes that rate as a fixed input to the procurement calculation; per-container dosing for tanks, jerrycans and tapstands is covered separately.

Why should a procurement plan add a wastage and buffer margin on top of the calculated tablet count?

Because delivered tablets and effectively used tablets are not the same number. A study of chlorinated water in South Sudan refugee camps found that 40 to 58% of households had no detectable residual chlorine in stored water despite tablets being distributed, and caseloads themselves swing sharply: WHO AFRO recorded weekly cases falling from an average of 1,000 at the December 2024 peak to 114 by late September 2025. Both are reasons to build a margin in rather than order to the bare arithmetic.

What is the shipping weight and volume of a large Aquatabs order?

The IFRC/ICRC Standard Products Catalogue lists a shipping weight of 0.0003kg and a shipping volume of 0.002 litres per 67mg NaDCC tablet, so multiplying the final tablet count by those figures gives the total consignment weight and volume before carton or pallet configuration is even confirmed.

Does holding Aquatabs stock in Juba reduce the safety stock a response needs?

Yes. A safety-stock buffer only needs to bridge the time to the next resupply, and that time is set by lead time, not by tablet count. Stock already in Juba is a dispatch measured in days rather than an import measured in weeks, which lets a programme carry a smaller buffer for the same level of protection, a distinction that matters more as response budgets tighten.